{"id":210,"date":"2022-05-18T16:37:34","date_gmt":"2022-05-18T16:37:34","guid":{"rendered":"https:\/\/pressbooks.ccconline.org\/accintrostats\/chapter\/continuous-probability-functions\/"},"modified":"2022-08-10T19:44:56","modified_gmt":"2022-08-10T19:44:56","slug":"continuous-probability-functions","status":"publish","type":"chapter","link":"https:\/\/pressbooks.ccconline.org\/accintrostats\/chapter\/continuous-probability-functions\/","title":{"raw":"Chapter 6.2: Continuous Probability Functions","rendered":"Chapter 6.2: Continuous Probability Functions"},"content":{"raw":"&nbsp;\r\n\r\nWe begin by defining a continuous probability density function. We use the function notation <em data-effect=\"italics\">f<\/em>(<em data-effect=\"italics\">x<\/em>). Intermediate algebra may have been your first formal introduction to functions. In the study of probability, the functions we study are special. We define the function <em data-effect=\"italics\">f<\/em>(<em data-effect=\"italics\">x<\/em>) so that the area between it and the x-axis is equal to a probability. Since the maximum probability is one, the maximum area is also one. <strong>For continuous probability distributions, PROBABILITY = AREA.<\/strong>\r\n<div class=\"textbox textbox--examples\" data-type=\"example\">\r\n<p id=\"element-630\">Consider the function <em data-effect=\"italics\">f<\/em>(<em data-effect=\"italics\">x<\/em>) = \\(\\frac{1}{20}\\) for 0 \u2264 <em data-effect=\"italics\">x<\/em> \u2264 20. <em data-effect=\"italics\">x<\/em> = a real number. The graph of <em data-effect=\"italics\">f<\/em>(<em data-effect=\"italics\">x<\/em>) = \\(\\frac{1}{20}\\) is a horizontal line. However, since 0 \u2264 <em data-effect=\"italics\">x<\/em> \u2264 20, <em data-effect=\"italics\">f<\/em>(<em data-effect=\"italics\">x<\/em>) is restricted to the portion between <em data-effect=\"italics\">x<\/em> = 0 and <em data-effect=\"italics\">x<\/em> = 20, inclusive.<\/p>\r\n\r\n<div id=\"fs-idm76319168\" class=\"bc-figure figure\"><span id=\"id39758796\" data-type=\"media\" data-alt=\"This shows the graph of the function f(x) = 1\/20. A horiztonal line ranges from the point (0, 1\/20) to the point (20, 1\/20). A vertical line extends from the x-axis to the end of the line at point (20, 1\/20) creating a rectangle.\"><img src=\"https:\/\/pressbooks.ccconline.org\/acccomposition1\/wp-content\/uploads\/sites\/83\/2022\/05\/fig-ch05_02_01-1.jpg\" alt=\"This shows the graph of the function f(x) = 1\/20. A horiztonal line ranges from the point (0, 1\/20) to the point (20, 1\/20). A vertical line extends from the x-axis to the end of the line at point (20, 1\/20) creating a rectangle.\" width=\"380\" data-media-type=\"image\/jpg\" \/><\/span><\/div>\r\n<p id=\"element-37\"><em data-effect=\"italics\">f<\/em>(<em data-effect=\"italics\">x<\/em>) = \\(\\frac{1}{20}\\)<strong>for<\/strong> 0 \u2264 <em data-effect=\"italics\">x<\/em> \u2264 20.<\/p>\r\nThe graph of <em data-effect=\"italics\">f<\/em>(<em data-effect=\"italics\">x<\/em>) = \\(\\frac{1}{20}\\) is a horizontal line segment when 0 \u2264 <em data-effect=\"italics\">x<\/em> \u2264 20.\r\n\r\nThe area between <em data-effect=\"italics\">f<\/em>(<em data-effect=\"italics\">x<\/em>) = \\(\\frac{1}{20}\\) where 0 \u2264 <em data-effect=\"italics\">x<\/em> \u2264 20 and the <em data-effect=\"italics\">x<\/em>-axis is the area of a rectangle with base = 20 and height = \\(\\frac{1}{20}\\).\r\n<div data-type=\"equation\">\\(\\text{AREA}=20\\left(\\frac{1}{20}\\right)=1\\)<\/div>\r\n<strong>Suppose we want to find the area between <em data-effect=\"italics\">f(<\/em><em data-effect=\"italics\">x<\/em>) = \\(\\frac{1}{20}\\) and the <em data-effect=\"italics\">x<\/em>-axis where 0 &lt; <em data-effect=\"italics\">x<\/em> &lt; 2.<\/strong>\r\n<div id=\"fs-idp91224976\" class=\"bc-figure figure\"><span id=\"id40073479\" data-type=\"media\" data-alt=\"This shows the graph of the function f(x) = 1\/20. A horiztonal line ranges from the point (0, 1\/20) to the point (20, 1\/20). A vertical line extends from the x-axis to the end of the line at point (20, 1\/20) creating a rectangle. A region is shaded inside the rectangle from x = 0 to x = 2.\"><img src=\"https:\/\/pressbooks.ccconline.org\/acccomposition1\/wp-content\/uploads\/sites\/83\/2022\/08\/fig-ch05_02_02-1.jpg\" alt=\"This shows the graph of the function f(x) = 1\/20. A horiztonal line ranges from the point (0, 1\/20) to the point (20, 1\/20). A vertical line extends from the x-axis to the end of the line at point (20, 1\/20) creating a rectangle. A region is shaded inside the rectangle from x = 0 to x = 2.\" width=\"380\" data-media-type=\"image\/jpg\" \/><\/span><\/div>\r\n\\(\\text{AREA\u00a0}=\\text{\u00a0}\\left(2\\text{\u00a0}\u2013\\text{\u00a0}0\\right)\\left(\\frac{1}{20}\\right)\\text{\u00a0}=\\text{\u00a0}0.1\\)\r\n\r\n\\(\\left(2\\text{}\u2013\\text{}0\\right)\\text{}=\\text{}2\\text{}=\\text{base of a rectangle}\\)\r\n<div data-type=\"note\" data-has-label=\"true\" data-label=\"\" data-element-type=\"Reminder\">\r\n<div data-type=\"title\">Reminder<\/div>\r\n<p id=\"eip-idp74119024\">area of a rectangle = (base)(height).<\/p>\r\n\r\n<\/div>\r\nThe area corresponds to a probability. The probability that <em data-effect=\"italics\">x<\/em> is between zero and two is 0.1, which can be written mathematically as <em data-effect=\"italics\">P<\/em>(0 &lt; <em data-effect=\"italics\">x<\/em> &lt; 2) = <em data-effect=\"italics\">P<\/em>(<em data-effect=\"italics\">x<\/em> &lt; 2) = 0.1.\r\n<p id=\"eip-553\"><strong>Suppose we want to find the area between <em data-effect=\"italics\">f<\/em>(<em data-effect=\"italics\">x<\/em>) = \\(\\frac{1}{20}\\) and the <em data-effect=\"italics\">x<\/em>-axis where 4 &lt; <em data-effect=\"italics\">x<\/em> &lt; 15.<\/strong><\/p>\r\n\r\n<div id=\"fs-idm39582736\" class=\"bc-figure figure\"><span id=\"id40137735\" data-type=\"media\" data-alt=\"This shows the graph of the function f(x) = 1\/20. A horiztonal line ranges from the point (0, 1\/20) to the point (20, 1\/20). A vertical line extends from the x-axis to the end of the line at point (20, 1\/20) creating a rectangle. A region is shaded inside the rectangle from x = 4 to x = 15.\"><img src=\"https:\/\/pressbooks.ccconline.org\/acccomposition1\/wp-content\/uploads\/sites\/83\/2022\/08\/fig-ch05_02_03-1.jpg\" alt=\"This shows the graph of the function f(x) = 1\/20. A horiztonal line ranges from the point (0, 1\/20) to the point (20, 1\/20). A vertical line extends from the x-axis to the end of the line at point (20, 1\/20) creating a rectangle. A region is shaded inside the rectangle from x = 4 to x = 15.\" width=\"380\" data-media-type=\"image\/jpg\" \/><\/span><\/div>\r\n<p id=\"fs-idm75475104\">\\(\\text{AREA\u00a0}=\\text{\u00a0}\\left(15\\text{\u00a0}\u2013\\text{\u00a0}4\\right)\\left(\\frac{1}{20}\\right)\\text{\u00a0}=\\text{\u00a0}0.55\\)<\/p>\r\n<p id=\"element-376\">\\(\\left(15\\text{\u00a0}\u2013\\text{\u00a0}4\\right)\\text{\u00a0}=\\text{\u00a0}11\\text{\u00a0}=\\text{\u00a0the\u00a0base\u00a0of\u00a0a\u00a0rectangle}\\)<\/p>\r\nThe area corresponds to the probability <em data-effect=\"italics\">P<\/em>(4 &lt; <em data-effect=\"italics\">x<\/em> &lt; 15) = 0.55.\r\n\r\nSuppose we want to find <em data-effect=\"italics\">P<\/em>(<em data-effect=\"italics\">x<\/em> = 15). On an x-y graph, <em data-effect=\"italics\">x<\/em> = 15 is a vertical line. A vertical line has no width (or zero width). Therefore, <em data-effect=\"italics\">P<\/em>(<em data-effect=\"italics\">x<\/em> = 15) = (base)(height) = (0)\\(\\left(\\frac{1}{20}\\right)\\) = 0\r\n<div id=\"fs-idm37512432\" class=\"bc-figure figure\"><span id=\"id40076640\" data-type=\"media\" data-alt=\"This shows the graph of the function f(x) = 1\/20. A horiztonal line ranges from the point (0, 1\/20) to the point (20, 1\/20). A vertical line extends from the x-axis to the end of the line at point (20, 1\/20) creating a rectangle. A vertical line extends from the horizontal axis to the graph at x = 15.\"><img src=\"https:\/\/pressbooks.ccconline.org\/acccomposition1\/wp-content\/uploads\/sites\/83\/2022\/08\/fig-ch05_02_04-1.jpg\" alt=\"This shows the graph of the function f(x) = 1\/20. A horiztonal line ranges from the point (0, 1\/20) to the point (20, 1\/20). A vertical line extends from the x-axis to the end of the line at point (20, 1\/20) creating a rectangle. A vertical line extends from the horizontal axis to the graph at x = 15.\" width=\"380\" data-media-type=\"image\/jpg\" \/><\/span><\/div>\r\n<em data-effect=\"italics\">P<\/em>(<em data-effect=\"italics\">X<\/em> \u2264 <em data-effect=\"italics\">x<\/em>), which can also be written as <em data-effect=\"italics\">P<\/em>(<em data-effect=\"italics\">X<\/em> &lt; <em data-effect=\"italics\">x<\/em>) for continuous distributions, is called the cumulative distribution function or CDF. Notice the \"less than or equal to\" symbol. We can also use the CDF to calculate <em data-effect=\"italics\">P<\/em>(<em data-effect=\"italics\">X<\/em> &gt; <em data-effect=\"italics\">x<\/em>). The CDF gives \"area to the left\" and <em data-effect=\"italics\">P<\/em>(<em data-effect=\"italics\">X<\/em> &gt; <em data-effect=\"italics\">x<\/em>) gives \"area to the right.\" We calculate <em data-effect=\"italics\">P<\/em>(<em data-effect=\"italics\">X<\/em> &gt; <em data-effect=\"italics\">x<\/em>) for continuous distributions as follows: <em data-effect=\"italics\">P<\/em>(<em data-effect=\"italics\">X<\/em> &gt; <em data-effect=\"italics\">x<\/em>) = 1 \u2013 <em data-effect=\"italics\">P<\/em> (<em data-effect=\"italics\">X<\/em> &lt; <em data-effect=\"italics\">x<\/em>).\r\n<div id=\"fs-idp12815264\" class=\"bc-figure figure\"><span id=\"id39508301\" data-type=\"media\" data-alt=\"This shows the graph of the function f(x) = 1\/20. A horiztonal line ranges from the point (0, 1\/20) to the point (20, 1\/20). A vertical line extends from the x-axis to the end of the line at point (20, 1\/20) creating a rectangle. The area to the left of a value, x, is shaded.\"><img src=\"https:\/\/pressbooks.ccconline.org\/acccomposition1\/wp-content\/uploads\/sites\/83\/2022\/08\/fig-ch05_02_05-1.jpg\" alt=\"This shows the graph of the function f(x) = 1\/20. A horiztonal line ranges from the point (0, 1\/20) to the point (20, 1\/20). A vertical line extends from the x-axis to the end of the line at point (20, 1\/20) creating a rectangle. The area to the left of a value, x, is shaded.\" width=\"380\" data-media-type=\"image\/jpg\" \/><\/span><\/div>\r\n<p id=\"element-473\">Label the graph with <em data-effect=\"italics\">f<\/em>(<em data-effect=\"italics\">x<\/em>) and <em data-effect=\"italics\">x<\/em>. Scale the <em data-effect=\"italics\">x<\/em> and <em data-effect=\"italics\">y<\/em> axes with the maximum <em data-effect=\"italics\">x<\/em> and <em data-effect=\"italics\">y<\/em> values. <em data-effect=\"italics\">f<\/em>(<em data-effect=\"italics\">x<\/em>) = \\(\\frac{1}{20}\\), 0 \u2264 <em data-effect=\"italics\">x<\/em> \u2264 20.<\/p>\r\n<p id=\"fs-idp36326688\">To calculate the probability that <em data-effect=\"italics\">x<\/em> is between two values, look at the following graph. Shade the region between <em data-effect=\"italics\">x<\/em> = 2.3 and <em data-effect=\"italics\">x<\/em> = 12.7. Then calculate the shaded area of a rectangle.<\/p>\r\n\r\n<div id=\"fs-idp96750640\" class=\"bc-figure figure\"><span id=\"id40140418\" data-type=\"media\" data-alt=\"This shows the graph of the function f(x) = 1\/20. A horiztonal line ranges from the point (0, 1\/20) to the point (20, 1\/20). A vertical line extends from the x-axis to the end of the line at point (20, 1\/20) creating a rectangle. A region is shaded inside the rectangle from x = 2.3 to x = 12.7\"><img src=\"https:\/\/pressbooks.ccconline.org\/acccomposition1\/wp-content\/uploads\/sites\/83\/2022\/08\/fig-ch05_02_06-1.jpg\" alt=\"This shows the graph of the function f(x) = 1\/20. A horiztonal line ranges from the point (0, 1\/20) to the point (20, 1\/20). A vertical line extends from the x-axis to the end of the line at point (20, 1\/20) creating a rectangle. A region is shaded inside the rectangle from x = 2.3 to x = 12.7\" width=\"380\" data-media-type=\"image\/jpg\" \/><\/span><\/div>\r\n<p id=\"element-979\">\\(P\\left(2.3&lt;x&lt;12.7\\right)=\\left(\\text{base}\\right)\\left(\\text{height}\\right)=\\left(12.7-2.3\\right)\\left(\\frac{1}{20}\\right)=0.52\\)<\/p>\r\n\r\n<\/div>\r\n<div id=\"fs-idm47598048\" class=\"statistics try\" data-type=\"note\" data-has-label=\"true\" data-label=\"\">\r\n<div data-type=\"title\">Try It<\/div>\r\n<div id=\"fs-idm81426464\" data-type=\"exercise\">\r\n<div id=\"fs-idm96151408\" data-type=\"problem\">\r\n<p id=\"fs-idp147477712\">Consider the function <em data-effect=\"italics\">f<\/em>(<em data-effect=\"italics\">x<\/em>) = \\(\\frac{\\text{1}}{8}\\) for 0 \u2264 <em data-effect=\"italics\">x<\/em> \u2264 8. Draw the graph of <em data-effect=\"italics\">f<\/em>(<em data-effect=\"italics\">x<\/em>) and find <em data-effect=\"italics\">P<\/em>(2.5 &lt; <em data-effect=\"italics\">x<\/em> &lt; 7.5).<\/p>\r\n\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<div id=\"fs-idp147304960\" class=\"summary\" data-depth=\"1\">\r\n<h3 data-type=\"title\">Chapter Review<\/h3>\r\n<p id=\"fs-idp147305600\">The probability density function (pdf) is used to describe probabilities for continuous random variables. The area under the density curve between two points corresponds to the probability that the variable falls between those two values. In other words, the area under the density curve between points <em data-effect=\"italics\">a<\/em> and <em data-effect=\"italics\">b<\/em> is equal to <em data-effect=\"italics\">P<\/em>(<em data-effect=\"italics\">a<\/em> &lt; <em data-effect=\"italics\">x<\/em> &lt; <em data-effect=\"italics\">b<\/em>). The cumulative distribution function (cdf) gives the probability as an area. If <em data-effect=\"italics\">X<\/em> is a continuous random variable, the probability density function (pdf), <em data-effect=\"italics\">f<\/em>(<em data-effect=\"italics\">x<\/em>), is used to draw the graph of the probability distribution. The total area under the graph of <em data-effect=\"italics\">f<\/em>(<em data-effect=\"italics\">x<\/em>) is one. The area under the graph of <em data-effect=\"italics\">f<\/em>(<em data-effect=\"italics\">x<\/em>) and between values <em data-effect=\"italics\">a<\/em> and <em data-effect=\"italics\">b<\/em> gives the probability <em data-effect=\"italics\">P<\/em>(<em data-effect=\"italics\">a<\/em> &lt; <em data-effect=\"italics\">x<\/em> &lt; <em data-effect=\"italics\">b<\/em>).<\/p>\r\n\r\n<div id=\"fs-idm60245824\" class=\"bc-figure figure\"><span id=\"fs-idp150656848\" data-type=\"media\" data-alt=\"The graph on the left shows a general density curve, y = f(x). The region under the curve and above the x-axis is shaded. The area of the shaded region is equal to 1. This shows that all possible outcomes are represented by the curve. The graph on the right shows the same density curve. Vertical lines x = a and x = b extend from the axis to the curve, and the area between the lines is shaded. The area of the shaded region represents the probabilit ythat a value x falls between a and b.\"><img src=\"https:\/\/pressbooks.ccconline.org\/acccomposition1\/wp-content\/uploads\/sites\/83\/2022\/08\/CNX_Stats_C05_M02_001-1.jpg\" alt=\"The graph on the left shows a general density curve, y = f(x). The region under the curve and above the x-axis is shaded. The area of the shaded region is equal to 1. This shows that all possible outcomes are represented by the curve. The graph on the right shows the same density curve. Vertical lines x = a and x = b extend from the axis to the curve, and the area between the lines is shaded. The area of the shaded region represents the probabilit ythat a value x falls between a and b.\" width=\"380\" data-media-type=\"image\/jpg\" \/><\/span><\/div>\r\n<p id=\"fs-idp108663296\">The cumulative distribution function (cdf) of <em data-effect=\"italics\">X<\/em> is defined by <em data-effect=\"italics\">P<\/em> (<em data-effect=\"italics\">X<\/em> \u2264 <em data-effect=\"italics\">x<\/em>). It is a function of <em data-effect=\"italics\">x<\/em> that gives the probability that the random variable is less than or equal to <em data-effect=\"italics\">x<\/em>.<\/p>\r\n\r\n<\/div>\r\n<div id=\"fs-idp108664192\" class=\"formula-review\" data-depth=\"1\">\r\n<h3 data-type=\"title\">Formula Review<\/h3>\r\n<p id=\"fs-idp125293440\">Probability density function (pdf) <em data-effect=\"italics\">f<\/em>(<em data-effect=\"italics\">x<\/em>):<\/p>\r\n\r\n<ul id=\"fs-idp125293824\">\r\n \t<li><em data-effect=\"italics\">f<\/em>(<em data-effect=\"italics\">x<\/em>) \u2265 0<\/li>\r\n \t<li>The total area under the curve <em data-effect=\"italics\">f<\/em>(<em data-effect=\"italics\">x<\/em>) is one.<\/li>\r\n<\/ul>\r\n<p id=\"fs-idp131806432\">Cumulative distribution function (cdf): <em data-effect=\"italics\">P<\/em>(<em data-effect=\"italics\">X<\/em> \u2264 <em data-effect=\"italics\">x<\/em>)<\/p>\r\n\r\n<\/div>\r\n<div id=\"fs-idm30315072\" class=\"practice\" data-depth=\"1\">\r\n<div id=\"eip-idm97087120\" data-type=\"exercise\">\r\n<div id=\"eip-idm97086864\" data-type=\"problem\">\r\n<p id=\"eip-idm97086608\">Which type of distribution does the graph illustrate?<\/p>\r\n\r\n<div id=\"eip-idm123385824\" class=\"bc-figure figure\"><span id=\"eip-idm123385568\" data-type=\"media\" data-alt=\"The horizontal axis ranges from 0 to 10. The distribution is modeled by a rectangle extending from x = 3 to x =8.\"><img src=\"https:\/\/pressbooks.ccconline.org\/acccomposition1\/wp-content\/uploads\/sites\/83\/2022\/08\/CNX_Stats_C05_M01_item001-1.jpg\" alt=\"The horizontal axis ranges from 0 to 10. The distribution is modeled by a rectangle extending from x = 3 to x =8.\" width=\"380\" data-media-type=\"image\/jpg\" \/><\/span><\/div>\r\n<\/div>\r\n<div id=\"eip-idm180418672\" data-type=\"solution\">\r\n<p id=\"eip-idm180418416\">Uniform Distribution<\/p>\r\n\r\n<\/div>\r\n<\/div>\r\n<div id=\"eip-idm18256352\" data-type=\"exercise\">\r\n<div id=\"eip-idm18256096\" data-type=\"problem\">\r\n<p id=\"eip-idm199212800\">Which type of distribution does the graph illustrate?<\/p>\r\n\r\n<div id=\"eip-idm199212416\" class=\"bc-figure figure\"><span id=\"eip-idm199212160\" data-type=\"media\" data-alt=\"This graph slopes downward. It begins at a point on the y-axis and approaches the x-axis at the right edge of the graph.\"><img src=\"https:\/\/pressbooks.ccconline.org\/acccomposition1\/wp-content\/uploads\/sites\/83\/2022\/08\/CNX_Stats_C05_M01_item002-1.jpg\" alt=\"This graph slopes downward. It begins at a point on the y-axis and approaches the x-axis at the right edge of the graph.\" width=\"380\" data-media-type=\"image\/jpg\" \/><\/span><\/div>\r\n<\/div>\r\n<\/div>\r\n<div id=\"eip-idm137825120\" data-type=\"exercise\">\r\n<div id=\"eip-idm143442320\" data-type=\"problem\">\r\n<p id=\"eip-idm143442064\">Which type of distribution does the graph illustrate?<\/p>\r\n\r\n<div id=\"eip-idm143441680\" class=\"bc-figure figure\"><span id=\"eip-idp45343472\" data-type=\"media\" data-alt=\"This graph shows a bell-shaped graph. The symmetric graph reaches maximum height at x = 0 and slopes downward gradually to the x-axis on each side of the peak.\"><img src=\"https:\/\/pressbooks.ccconline.org\/acccomposition1\/wp-content\/uploads\/sites\/83\/2022\/08\/CNX_Stats_C05_M01_item003-1.jpg\" alt=\"This graph shows a bell-shaped graph. The symmetric graph reaches maximum height at x = 0 and slopes downward gradually to the x-axis on each side of the peak.\" width=\"380\" data-media-type=\"image\/jpg\" \/><\/span><\/div>\r\n<\/div>\r\n<div id=\"eip-idm191766752\" data-type=\"solution\">\r\n<p id=\"eip-idm70312624\">Normal Distribution<\/p>\r\n\r\n<\/div>\r\n<\/div>\r\n<div id=\"eip-idm170433264\" data-type=\"exercise\">\r\n<div id=\"eip-idm170433008\" data-type=\"problem\">\r\n<p id=\"eip-idm170432752\">What does the shaded area represent? <em data-effect=\"italics\">P<\/em>(___&lt; <em data-effect=\"italics\">x<\/em> &lt; ___)<\/p>\r\n\r\n<div id=\"eip-idp7874608\" class=\"bc-figure figure\"><span id=\"eip-idm79769968\" data-type=\"media\" data-alt=\"This graph shows a uniform distribution. The horizontal axis ranges from 0 to 10. The distribution is modeled by a rectangle extending from x = 1 to x = 8. A region from x = 2 to x = 5 is shaded inside the rectangle.\"><img src=\"https:\/\/pressbooks.ccconline.org\/acccomposition1\/wp-content\/uploads\/sites\/83\/2022\/08\/CNX_Stats_C05_M01_item004-1.jpg\" alt=\"This graph shows a uniform distribution. The horizontal axis ranges from 0 to 10. The distribution is modeled by a rectangle extending from x = 1 to x = 8. A region from x = 2 to x = 5 is shaded inside the rectangle.\" width=\"380\" data-media-type=\"image\/jpg\" \/><\/span><\/div>\r\n<\/div>\r\n<\/div>\r\n<div id=\"eip-idm160222016\" data-type=\"exercise\">\r\n<div id=\"eip-idm40131600\" data-type=\"problem\">\r\n<p id=\"eip-idm40131344\">What does the shaded area represent? <em data-effect=\"italics\">P<\/em>(___&lt; <em data-effect=\"italics\">x<\/em> &lt; ___)<\/p>\r\n\r\n<div id=\"eip-idm126372688\" class=\"bc-figure figure\"><span id=\"eip-idm126372432\" data-type=\"media\" data-alt=\"This graph shows an exponential distribution. The graph slopes downward. It begins at a point on the y-axis and approaches the x-axis at the right edge of the graph. The region under the graph from x = 6 to x = 7 is shaded.\"><img src=\"https:\/\/pressbooks.ccconline.org\/acccomposition1\/wp-content\/uploads\/sites\/83\/2022\/08\/CNX_Stats_C05_M01_item005-1.jpg\" alt=\"This graph shows an exponential distribution. The graph slopes downward. It begins at a point on the y-axis and approaches the x-axis at the right edge of the graph. The region under the graph from x = 6 to x = 7 is shaded.\" width=\"380\" data-media-type=\"image\/jpg\" \/><\/span><\/div>\r\n<\/div>\r\n<div id=\"eip-idm164759504\" data-type=\"solution\">\r\n<p id=\"eip-idm59247088\"><em data-effect=\"italics\">P<\/em>(6 &lt; <em data-effect=\"italics\">x<\/em> &lt; 7)<\/p>\r\n\r\n<\/div>\r\n<\/div>\r\n<div id=\"fs-idm118866416\" data-type=\"exercise\">\r\n<div id=\"fs-idm94113008\" data-type=\"problem\">\r\n<p id=\"fs-idm186932672\">For a continuous probablity distribution, 0 \u2264 <em data-effect=\"italics\">x<\/em> \u2264 15. What is <em data-effect=\"italics\">P<\/em>(<em data-effect=\"italics\">x<\/em> &gt; 15)?<\/p>\r\n\r\n<\/div>\r\n<\/div>\r\n<div id=\"fs-idm154014752\" data-type=\"exercise\">\r\n<div id=\"fs-idm158384896\" data-type=\"problem\">\r\n<p id=\"fs-idm174567168\">What is the area under <em data-effect=\"italics\">f<\/em>(<em data-effect=\"italics\">x<\/em>) if the function is a continuous probability density function?<\/p>\r\n\r\n<\/div>\r\n<div id=\"fs-idm96621808\" data-type=\"solution\">\r\n<p id=\"fs-idm101963728\">one<\/p>\r\n\r\n<\/div>\r\n<\/div>\r\n<div id=\"fs-idm159828512\" data-type=\"exercise\">\r\n<div id=\"fs-idm28635392\" data-type=\"problem\">\r\n<p id=\"fs-idm44266992\">For a continuous probability distribution, 0 \u2264 <em data-effect=\"italics\">x<\/em> \u2264 10. What is <em data-effect=\"italics\">P<\/em>(<em data-effect=\"italics\">x<\/em> = 7)?<\/p>\r\n\r\n<\/div>\r\n<\/div>\r\n<div id=\"fs-idm89415120\" data-type=\"exercise\">\r\n<div id=\"fs-idm119661456\" data-type=\"problem\">\r\n<p id=\"fs-idm114444880\">A <strong>continuous<\/strong> probability function is restricted to the portion between <em data-effect=\"italics\">x<\/em> = 0 and 7. What is <em data-effect=\"italics\">P<\/em>(<em data-effect=\"italics\">x<\/em> = 10)?<\/p>\r\n\r\n<\/div>\r\n<div id=\"fs-idm29287760\" data-type=\"solution\">\r\n<p id=\"fs-idm160336672\">zero<\/p>\r\n\r\n<\/div>\r\n<\/div>\r\n<div id=\"fs-idm185391792\" data-type=\"exercise\">\r\n<div id=\"fs-idm70578720\" data-type=\"problem\">\r\n<p id=\"fs-idm83804704\"><em data-effect=\"italics\">f<\/em>(<em data-effect=\"italics\">x<\/em>) for a continuous probability function is \\(\\frac{1}{5}\\), and the function is restricted to 0 \u2264 <em data-effect=\"italics\">x<\/em> \u2264 5. What is <em data-effect=\"italics\">P<\/em>(<em data-effect=\"italics\">x<\/em> &lt; 0)?<\/p>\r\n\r\n<\/div>\r\n<\/div>\r\n<div id=\"fs-idm78277152\" data-type=\"exercise\">\r\n<div id=\"fs-idm119655680\" data-type=\"problem\">\r\n<p id=\"fs-idm107695264\"><em data-effect=\"italics\">f<\/em>(<em data-effect=\"italics\">x<\/em>), a continuous probability function, is equal to \\(\\frac{1}{12}\\), and the function is restricted to 0 \u2264 <em data-effect=\"italics\">x<\/em> \u2264 12. What is <em data-effect=\"italics\">P<\/em> (0 &lt; <em data-effect=\"italics\">x<\/em> &lt; 12)?<\/p>\r\n\r\n<\/div>\r\n<div id=\"fs-idm109882608\" data-type=\"solution\">\r\n<p id=\"fs-idm185543600\">one<\/p>\r\n\r\n<\/div>\r\n<\/div>\r\n<div id=\"fs-idm31115936\" data-type=\"exercise\">\r\n<div id=\"fs-idm126442096\" data-type=\"problem\">\r\n<p id=\"fs-idm79659008\">Find the probability that <em data-effect=\"italics\">x<\/em> falls in the shaded area.<\/p>\r\n\r\n<div id=\"fs-idm29576816\" class=\"bc-figure figure\"><span id=\"fs-idm168532640\" data-type=\"media\" data-alt=\"\"><img src=\"https:\/\/pressbooks.ccconline.org\/acccomposition1\/wp-content\/uploads\/sites\/83\/2022\/08\/CNX_Stats_C05_M02_item001-1.jpg\" alt=\"\" width=\"380\" data-media-type=\"image\/jpg\" \/><\/span><\/div>\r\n<\/div>\r\n<\/div>\r\n<div id=\"fs-idm29257104\" data-type=\"exercise\">\r\n<div id=\"fs-idm70564992\" data-type=\"problem\">\r\n<p id=\"fs-idm5797792\">Find the probability that <em data-effect=\"italics\">x<\/em> falls in the shaded area.<\/p>\r\n\r\n<div id=\"fs-idm120132416\" class=\"bc-figure figure\"><span id=\"fs-idm17039824\" data-type=\"media\" data-alt=\"\"><img src=\"https:\/\/pressbooks.ccconline.org\/acccomposition1\/wp-content\/uploads\/sites\/83\/2022\/08\/CNX_Stats_C05_M02_item002-1.jpg\" alt=\"\" width=\"380\" data-media-type=\"image\/jpg\" \/><\/span><\/div>\r\n<\/div>\r\n<div id=\"fs-idm192509264\" data-type=\"solution\">\r\n<p id=\"fs-idm100002320\">0.625<\/p>\r\n\r\n<\/div>\r\n<\/div>\r\n<div id=\"fs-idm144329792\" data-type=\"exercise\">\r\n<div id=\"fs-idm109804912\" data-type=\"problem\">\r\n<p id=\"fs-idp1777728\">Find the probability that <em data-effect=\"italics\">x<\/em> falls in the shaded area.<\/p>\r\n\r\n<div id=\"fs-idm167436128\" class=\"bc-figure figure\"><span id=\"fs-idm163441712\" data-type=\"media\" data-alt=\"\"><img src=\"https:\/\/pressbooks.ccconline.org\/acccomposition1\/wp-content\/uploads\/sites\/83\/2022\/08\/CNX_Stats_C05_M02_item003-1.jpg\" alt=\"\" width=\"380\" data-media-type=\"image\/jpg\" \/><\/span><\/div>\r\n<\/div>\r\n<\/div>\r\n<div id=\"fs-idm170928704\" data-type=\"exercise\">\r\n<div id=\"fs-idm76313888\" data-type=\"problem\">\r\n<p id=\"fs-idm73539776\"><em data-effect=\"italics\">f<\/em>(<em data-effect=\"italics\">x<\/em>), a continuous probability function, is equal to \\(\\frac{1}{3}\\) and the function is restricted to 1 \u2264 <em data-effect=\"italics\">x<\/em> \u2264 4. Describe \\(P\\left(x&gt;\\frac{3}{2}\\right).\\)<\/p>\r\n\r\n<\/div>\r\n<div id=\"fs-idm63500944\" data-type=\"solution\">\r\n<p id=\"fs-idm21180864\">The probability is equal to the area from <em data-effect=\"italics\">x<\/em> = \\(\\frac{3}{2}\\) to <em data-effect=\"italics\">x<\/em> = 4 above the x-axis and up to <em data-effect=\"italics\">f<\/em>(<em data-effect=\"italics\">x<\/em>) = \\(\\frac{1}{3}\\).<\/p>\r\n\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<div id=\"fs-idp5416000\" class=\"free-response\" data-depth=\"1\">\r\n<h3 data-type=\"title\">Homework<\/h3>\r\n<p id=\"eip-idm57931200\"><em data-effect=\"italics\">For each probability and percentile problem, draw the picture.<\/em><\/p>\r\n\r\n<div id=\"eip-idp84147744\" data-type=\"exercise\">\r\n<div id=\"eip-idp84148000\" data-type=\"problem\">\r\n<p id=\"eip-idp36661712\">1) <span style=\"font-size: 1em\">When age is rounded to the nearest year, do the data stay continuous, or do they become discrete? \u00a0Why?<\/span><\/p>\r\n\r\n<\/div>\r\n<\/div>\r\n<div id=\"eip-idm16922624\" data-type=\"exercise\">\r\n<div id=\"eip-idm19380464\" data-type=\"solution\">\r\n\r\n2) Consider the following experiment. You are one of 100 people enlisted to take part in a study to determine the percent of nurses in America with an R.N. (registered nurse) degree. \u00a0You ask nurses if they have an R.N. degree. \u00a0The nurses answer \u201cyes\u201d or \u201cno.\u201d \u00a0You then calculate the percentage of nurses with an R.N. degree. \u00a0You give that percentage to your supervisor.\r\n<ol id=\"eip-idp36662096\" type=\"a\">\r\n \t<li>What part of the experiment will yield discrete data?<\/li>\r\n \t<li>What part of the experiment will yield continuous data?<\/li>\r\n<\/ol>\r\n<strong>Answers to odd questions<\/strong>\r\n\r\n1) Age is a measurement, regardless of the accuracy used.\r\n\r\n<\/div>\r\n<\/div>\r\n<\/div>","rendered":"<p>&nbsp;<\/p>\n<p>We begin by defining a continuous probability density function. We use the function notation <em data-effect=\"italics\">f<\/em>(<em data-effect=\"italics\">x<\/em>). Intermediate algebra may have been your first formal introduction to functions. In the study of probability, the functions we study are special. We define the function <em data-effect=\"italics\">f<\/em>(<em data-effect=\"italics\">x<\/em>) so that the area between it and the x-axis is equal to a probability. Since the maximum probability is one, the maximum area is also one. <strong>For continuous probability distributions, PROBABILITY = AREA.<\/strong><\/p>\n<div class=\"textbox textbox--examples\" data-type=\"example\">\n<p id=\"element-630\">Consider the function <em data-effect=\"italics\">f<\/em>(<em data-effect=\"italics\">x<\/em>) = \\(\\frac{1}{20}\\) for 0 \u2264 <em data-effect=\"italics\">x<\/em> \u2264 20. <em data-effect=\"italics\">x<\/em> = a real number. The graph of <em data-effect=\"italics\">f<\/em>(<em data-effect=\"italics\">x<\/em>) = \\(\\frac{1}{20}\\) is a horizontal line. However, since 0 \u2264 <em data-effect=\"italics\">x<\/em> \u2264 20, <em data-effect=\"italics\">f<\/em>(<em data-effect=\"italics\">x<\/em>) is restricted to the portion between <em data-effect=\"italics\">x<\/em> = 0 and <em data-effect=\"italics\">x<\/em> = 20, inclusive.<\/p>\n<div id=\"fs-idm76319168\" class=\"bc-figure figure\"><span id=\"id39758796\" data-type=\"media\" data-alt=\"This shows the graph of the function f(x) = 1\/20. A horiztonal line ranges from the point (0, 1\/20) to the point (20, 1\/20). A vertical line extends from the x-axis to the end of the line at point (20, 1\/20) creating a rectangle.\"><img decoding=\"async\" src=\"https:\/\/pressbooks.ccconline.org\/acccomposition1\/wp-content\/uploads\/sites\/83\/2022\/05\/fig-ch05_02_01-1.jpg\" alt=\"This shows the graph of the function f(x) = 1\/20. A horiztonal line ranges from the point (0, 1\/20) to the point (20, 1\/20). A vertical line extends from the x-axis to the end of the line at point (20, 1\/20) creating a rectangle.\" width=\"380\" data-media-type=\"image\/jpg\" \/><\/span><\/div>\n<p id=\"element-37\"><em data-effect=\"italics\">f<\/em>(<em data-effect=\"italics\">x<\/em>) = \\(\\frac{1}{20}\\)<strong>for<\/strong> 0 \u2264 <em data-effect=\"italics\">x<\/em> \u2264 20.<\/p>\n<p>The graph of <em data-effect=\"italics\">f<\/em>(<em data-effect=\"italics\">x<\/em>) = \\(\\frac{1}{20}\\) is a horizontal line segment when 0 \u2264 <em data-effect=\"italics\">x<\/em> \u2264 20.<\/p>\n<p>The area between <em data-effect=\"italics\">f<\/em>(<em data-effect=\"italics\">x<\/em>) = \\(\\frac{1}{20}\\) where 0 \u2264 <em data-effect=\"italics\">x<\/em> \u2264 20 and the <em data-effect=\"italics\">x<\/em>-axis is the area of a rectangle with base = 20 and height = \\(\\frac{1}{20}\\).<\/p>\n<div data-type=\"equation\">\\(\\text{AREA}=20\\left(\\frac{1}{20}\\right)=1\\)<\/div>\n<p><strong>Suppose we want to find the area between <em data-effect=\"italics\">f(<\/em><em data-effect=\"italics\">x<\/em>) = \\(\\frac{1}{20}\\) and the <em data-effect=\"italics\">x<\/em>-axis where 0 &lt; <em data-effect=\"italics\">x<\/em> &lt; 2.<\/strong><\/p>\n<div id=\"fs-idp91224976\" class=\"bc-figure figure\"><span id=\"id40073479\" data-type=\"media\" data-alt=\"This shows the graph of the function f(x) = 1\/20. A horiztonal line ranges from the point (0, 1\/20) to the point (20, 1\/20). A vertical line extends from the x-axis to the end of the line at point (20, 1\/20) creating a rectangle. A region is shaded inside the rectangle from x = 0 to x = 2.\"><img decoding=\"async\" src=\"https:\/\/pressbooks.ccconline.org\/acccomposition1\/wp-content\/uploads\/sites\/83\/2022\/08\/fig-ch05_02_02-1.jpg\" alt=\"This shows the graph of the function f(x) = 1\/20. A horiztonal line ranges from the point (0, 1\/20) to the point (20, 1\/20). A vertical line extends from the x-axis to the end of the line at point (20, 1\/20) creating a rectangle. A region is shaded inside the rectangle from x = 0 to x = 2.\" width=\"380\" data-media-type=\"image\/jpg\" \/><\/span><\/div>\n<p>\\(\\text{AREA\u00a0}=\\text{\u00a0}\\left(2\\text{\u00a0}\u2013\\text{\u00a0}0\\right)\\left(\\frac{1}{20}\\right)\\text{\u00a0}=\\text{\u00a0}0.1\\)<\/p>\n<p>\\(\\left(2\\text{}\u2013\\text{}0\\right)\\text{}=\\text{}2\\text{}=\\text{base of a rectangle}\\)<\/p>\n<div data-type=\"note\" data-has-label=\"true\" data-label=\"\" data-element-type=\"Reminder\">\n<div data-type=\"title\">Reminder<\/div>\n<p id=\"eip-idp74119024\">area of a rectangle = (base)(height).<\/p>\n<\/div>\n<p>The area corresponds to a probability. The probability that <em data-effect=\"italics\">x<\/em> is between zero and two is 0.1, which can be written mathematically as <em data-effect=\"italics\">P<\/em>(0 &lt; <em data-effect=\"italics\">x<\/em> &lt; 2) = <em data-effect=\"italics\">P<\/em>(<em data-effect=\"italics\">x<\/em> &lt; 2) = 0.1.<\/p>\n<p id=\"eip-553\"><strong>Suppose we want to find the area between <em data-effect=\"italics\">f<\/em>(<em data-effect=\"italics\">x<\/em>) = \\(\\frac{1}{20}\\) and the <em data-effect=\"italics\">x<\/em>-axis where 4 &lt; <em data-effect=\"italics\">x<\/em> &lt; 15.<\/strong><\/p>\n<div id=\"fs-idm39582736\" class=\"bc-figure figure\"><span id=\"id40137735\" data-type=\"media\" data-alt=\"This shows the graph of the function f(x) = 1\/20. A horiztonal line ranges from the point (0, 1\/20) to the point (20, 1\/20). A vertical line extends from the x-axis to the end of the line at point (20, 1\/20) creating a rectangle. A region is shaded inside the rectangle from x = 4 to x = 15.\"><img decoding=\"async\" src=\"https:\/\/pressbooks.ccconline.org\/acccomposition1\/wp-content\/uploads\/sites\/83\/2022\/08\/fig-ch05_02_03-1.jpg\" alt=\"This shows the graph of the function f(x) = 1\/20. A horiztonal line ranges from the point (0, 1\/20) to the point (20, 1\/20). A vertical line extends from the x-axis to the end of the line at point (20, 1\/20) creating a rectangle. A region is shaded inside the rectangle from x = 4 to x = 15.\" width=\"380\" data-media-type=\"image\/jpg\" \/><\/span><\/div>\n<p id=\"fs-idm75475104\">\\(\\text{AREA\u00a0}=\\text{\u00a0}\\left(15\\text{\u00a0}\u2013\\text{\u00a0}4\\right)\\left(\\frac{1}{20}\\right)\\text{\u00a0}=\\text{\u00a0}0.55\\)<\/p>\n<p id=\"element-376\">\\(\\left(15\\text{\u00a0}\u2013\\text{\u00a0}4\\right)\\text{\u00a0}=\\text{\u00a0}11\\text{\u00a0}=\\text{\u00a0the\u00a0base\u00a0of\u00a0a\u00a0rectangle}\\)<\/p>\n<p>The area corresponds to the probability <em data-effect=\"italics\">P<\/em>(4 &lt; <em data-effect=\"italics\">x<\/em> &lt; 15) = 0.55.<\/p>\n<p>Suppose we want to find <em data-effect=\"italics\">P<\/em>(<em data-effect=\"italics\">x<\/em> = 15). On an x-y graph, <em data-effect=\"italics\">x<\/em> = 15 is a vertical line. A vertical line has no width (or zero width). Therefore, <em data-effect=\"italics\">P<\/em>(<em data-effect=\"italics\">x<\/em> = 15) = (base)(height) = (0)\\(\\left(\\frac{1}{20}\\right)\\) = 0<\/p>\n<div id=\"fs-idm37512432\" class=\"bc-figure figure\"><span id=\"id40076640\" data-type=\"media\" data-alt=\"This shows the graph of the function f(x) = 1\/20. A horiztonal line ranges from the point (0, 1\/20) to the point (20, 1\/20). A vertical line extends from the x-axis to the end of the line at point (20, 1\/20) creating a rectangle. A vertical line extends from the horizontal axis to the graph at x = 15.\"><img decoding=\"async\" src=\"https:\/\/pressbooks.ccconline.org\/acccomposition1\/wp-content\/uploads\/sites\/83\/2022\/08\/fig-ch05_02_04-1.jpg\" alt=\"This shows the graph of the function f(x) = 1\/20. A horiztonal line ranges from the point (0, 1\/20) to the point (20, 1\/20). A vertical line extends from the x-axis to the end of the line at point (20, 1\/20) creating a rectangle. A vertical line extends from the horizontal axis to the graph at x = 15.\" width=\"380\" data-media-type=\"image\/jpg\" \/><\/span><\/div>\n<p><em data-effect=\"italics\">P<\/em>(<em data-effect=\"italics\">X<\/em> \u2264 <em data-effect=\"italics\">x<\/em>), which can also be written as <em data-effect=\"italics\">P<\/em>(<em data-effect=\"italics\">X<\/em> &lt; <em data-effect=\"italics\">x<\/em>) for continuous distributions, is called the cumulative distribution function or CDF. Notice the &#8220;less than or equal to&#8221; symbol. We can also use the CDF to calculate <em data-effect=\"italics\">P<\/em>(<em data-effect=\"italics\">X<\/em> &gt; <em data-effect=\"italics\">x<\/em>). The CDF gives &#8220;area to the left&#8221; and <em data-effect=\"italics\">P<\/em>(<em data-effect=\"italics\">X<\/em> &gt; <em data-effect=\"italics\">x<\/em>) gives &#8220;area to the right.&#8221; We calculate <em data-effect=\"italics\">P<\/em>(<em data-effect=\"italics\">X<\/em> &gt; <em data-effect=\"italics\">x<\/em>) for continuous distributions as follows: <em data-effect=\"italics\">P<\/em>(<em data-effect=\"italics\">X<\/em> &gt; <em data-effect=\"italics\">x<\/em>) = 1 \u2013 <em data-effect=\"italics\">P<\/em> (<em data-effect=\"italics\">X<\/em> &lt; <em data-effect=\"italics\">x<\/em>).<\/p>\n<div id=\"fs-idp12815264\" class=\"bc-figure figure\"><span id=\"id39508301\" data-type=\"media\" data-alt=\"This shows the graph of the function f(x) = 1\/20. A horiztonal line ranges from the point (0, 1\/20) to the point (20, 1\/20). A vertical line extends from the x-axis to the end of the line at point (20, 1\/20) creating a rectangle. The area to the left of a value, x, is shaded.\"><img decoding=\"async\" src=\"https:\/\/pressbooks.ccconline.org\/acccomposition1\/wp-content\/uploads\/sites\/83\/2022\/08\/fig-ch05_02_05-1.jpg\" alt=\"This shows the graph of the function f(x) = 1\/20. A horiztonal line ranges from the point (0, 1\/20) to the point (20, 1\/20). A vertical line extends from the x-axis to the end of the line at point (20, 1\/20) creating a rectangle. The area to the left of a value, x, is shaded.\" width=\"380\" data-media-type=\"image\/jpg\" \/><\/span><\/div>\n<p id=\"element-473\">Label the graph with <em data-effect=\"italics\">f<\/em>(<em data-effect=\"italics\">x<\/em>) and <em data-effect=\"italics\">x<\/em>. Scale the <em data-effect=\"italics\">x<\/em> and <em data-effect=\"italics\">y<\/em> axes with the maximum <em data-effect=\"italics\">x<\/em> and <em data-effect=\"italics\">y<\/em> values. <em data-effect=\"italics\">f<\/em>(<em data-effect=\"italics\">x<\/em>) = \\(\\frac{1}{20}\\), 0 \u2264 <em data-effect=\"italics\">x<\/em> \u2264 20.<\/p>\n<p id=\"fs-idp36326688\">To calculate the probability that <em data-effect=\"italics\">x<\/em> is between two values, look at the following graph. Shade the region between <em data-effect=\"italics\">x<\/em> = 2.3 and <em data-effect=\"italics\">x<\/em> = 12.7. Then calculate the shaded area of a rectangle.<\/p>\n<div id=\"fs-idp96750640\" class=\"bc-figure figure\"><span id=\"id40140418\" data-type=\"media\" data-alt=\"This shows the graph of the function f(x) = 1\/20. A horiztonal line ranges from the point (0, 1\/20) to the point (20, 1\/20). A vertical line extends from the x-axis to the end of the line at point (20, 1\/20) creating a rectangle. A region is shaded inside the rectangle from x = 2.3 to x = 12.7\"><img decoding=\"async\" src=\"https:\/\/pressbooks.ccconline.org\/acccomposition1\/wp-content\/uploads\/sites\/83\/2022\/08\/fig-ch05_02_06-1.jpg\" alt=\"This shows the graph of the function f(x) = 1\/20. A horiztonal line ranges from the point (0, 1\/20) to the point (20, 1\/20). A vertical line extends from the x-axis to the end of the line at point (20, 1\/20) creating a rectangle. A region is shaded inside the rectangle from x = 2.3 to x = 12.7\" width=\"380\" data-media-type=\"image\/jpg\" \/><\/span><\/div>\n<p id=\"element-979\">\\(P\\left(2.3&lt;x&lt;12.7\\right)=\\left(\\text{base}\\right)\\left(\\text{height}\\right)=\\left(12.7-2.3\\right)\\left(\\frac{1}{20}\\right)=0.52\\)<\/p>\n<\/div>\n<div id=\"fs-idm47598048\" class=\"statistics try\" data-type=\"note\" data-has-label=\"true\" data-label=\"\">\n<div data-type=\"title\">Try It<\/div>\n<div id=\"fs-idm81426464\" data-type=\"exercise\">\n<div id=\"fs-idm96151408\" data-type=\"problem\">\n<p id=\"fs-idp147477712\">Consider the function <em data-effect=\"italics\">f<\/em>(<em data-effect=\"italics\">x<\/em>) = \\(\\frac{\\text{1}}{8}\\) for 0 \u2264 <em data-effect=\"italics\">x<\/em> \u2264 8. Draw the graph of <em data-effect=\"italics\">f<\/em>(<em data-effect=\"italics\">x<\/em>) and find <em data-effect=\"italics\">P<\/em>(2.5 &lt; <em data-effect=\"italics\">x<\/em> &lt; 7.5).<\/p>\n<\/div>\n<\/div>\n<\/div>\n<div id=\"fs-idp147304960\" class=\"summary\" data-depth=\"1\">\n<h3 data-type=\"title\">Chapter Review<\/h3>\n<p id=\"fs-idp147305600\">The probability density function (pdf) is used to describe probabilities for continuous random variables. The area under the density curve between two points corresponds to the probability that the variable falls between those two values. In other words, the area under the density curve between points <em data-effect=\"italics\">a<\/em> and <em data-effect=\"italics\">b<\/em> is equal to <em data-effect=\"italics\">P<\/em>(<em data-effect=\"italics\">a<\/em> &lt; <em data-effect=\"italics\">x<\/em> &lt; <em data-effect=\"italics\">b<\/em>). The cumulative distribution function (cdf) gives the probability as an area. If <em data-effect=\"italics\">X<\/em> is a continuous random variable, the probability density function (pdf), <em data-effect=\"italics\">f<\/em>(<em data-effect=\"italics\">x<\/em>), is used to draw the graph of the probability distribution. The total area under the graph of <em data-effect=\"italics\">f<\/em>(<em data-effect=\"italics\">x<\/em>) is one. The area under the graph of <em data-effect=\"italics\">f<\/em>(<em data-effect=\"italics\">x<\/em>) and between values <em data-effect=\"italics\">a<\/em> and <em data-effect=\"italics\">b<\/em> gives the probability <em data-effect=\"italics\">P<\/em>(<em data-effect=\"italics\">a<\/em> &lt; <em data-effect=\"italics\">x<\/em> &lt; <em data-effect=\"italics\">b<\/em>).<\/p>\n<div id=\"fs-idm60245824\" class=\"bc-figure figure\"><span id=\"fs-idp150656848\" data-type=\"media\" data-alt=\"The graph on the left shows a general density curve, y = f(x). The region under the curve and above the x-axis is shaded. The area of the shaded region is equal to 1. This shows that all possible outcomes are represented by the curve. The graph on the right shows the same density curve. Vertical lines x = a and x = b extend from the axis to the curve, and the area between the lines is shaded. The area of the shaded region represents the probabilit ythat a value x falls between a and b.\"><img decoding=\"async\" src=\"https:\/\/pressbooks.ccconline.org\/acccomposition1\/wp-content\/uploads\/sites\/83\/2022\/08\/CNX_Stats_C05_M02_001-1.jpg\" alt=\"The graph on the left shows a general density curve, y = f(x). The region under the curve and above the x-axis is shaded. The area of the shaded region is equal to 1. This shows that all possible outcomes are represented by the curve. The graph on the right shows the same density curve. Vertical lines x = a and x = b extend from the axis to the curve, and the area between the lines is shaded. The area of the shaded region represents the probabilit ythat a value x falls between a and b.\" width=\"380\" data-media-type=\"image\/jpg\" \/><\/span><\/div>\n<p id=\"fs-idp108663296\">The cumulative distribution function (cdf) of <em data-effect=\"italics\">X<\/em> is defined by <em data-effect=\"italics\">P<\/em> (<em data-effect=\"italics\">X<\/em> \u2264 <em data-effect=\"italics\">x<\/em>). It is a function of <em data-effect=\"italics\">x<\/em> that gives the probability that the random variable is less than or equal to <em data-effect=\"italics\">x<\/em>.<\/p>\n<\/div>\n<div id=\"fs-idp108664192\" class=\"formula-review\" data-depth=\"1\">\n<h3 data-type=\"title\">Formula Review<\/h3>\n<p id=\"fs-idp125293440\">Probability density function (pdf) <em data-effect=\"italics\">f<\/em>(<em data-effect=\"italics\">x<\/em>):<\/p>\n<ul id=\"fs-idp125293824\">\n<li><em data-effect=\"italics\">f<\/em>(<em data-effect=\"italics\">x<\/em>) \u2265 0<\/li>\n<li>The total area under the curve <em data-effect=\"italics\">f<\/em>(<em data-effect=\"italics\">x<\/em>) is one.<\/li>\n<\/ul>\n<p id=\"fs-idp131806432\">Cumulative distribution function (cdf): <em data-effect=\"italics\">P<\/em>(<em data-effect=\"italics\">X<\/em> \u2264 <em data-effect=\"italics\">x<\/em>)<\/p>\n<\/div>\n<div id=\"fs-idm30315072\" class=\"practice\" data-depth=\"1\">\n<div id=\"eip-idm97087120\" data-type=\"exercise\">\n<div id=\"eip-idm97086864\" data-type=\"problem\">\n<p id=\"eip-idm97086608\">Which type of distribution does the graph illustrate?<\/p>\n<div id=\"eip-idm123385824\" class=\"bc-figure figure\"><span id=\"eip-idm123385568\" data-type=\"media\" data-alt=\"The horizontal axis ranges from 0 to 10. The distribution is modeled by a rectangle extending from x = 3 to x =8.\"><img decoding=\"async\" src=\"https:\/\/pressbooks.ccconline.org\/acccomposition1\/wp-content\/uploads\/sites\/83\/2022\/08\/CNX_Stats_C05_M01_item001-1.jpg\" alt=\"The horizontal axis ranges from 0 to 10. The distribution is modeled by a rectangle extending from x = 3 to x =8.\" width=\"380\" data-media-type=\"image\/jpg\" \/><\/span><\/div>\n<\/div>\n<div id=\"eip-idm180418672\" data-type=\"solution\">\n<p id=\"eip-idm180418416\">Uniform Distribution<\/p>\n<\/div>\n<\/div>\n<div id=\"eip-idm18256352\" data-type=\"exercise\">\n<div id=\"eip-idm18256096\" data-type=\"problem\">\n<p id=\"eip-idm199212800\">Which type of distribution does the graph illustrate?<\/p>\n<div id=\"eip-idm199212416\" class=\"bc-figure figure\"><span id=\"eip-idm199212160\" data-type=\"media\" data-alt=\"This graph slopes downward. It begins at a point on the y-axis and approaches the x-axis at the right edge of the graph.\"><img decoding=\"async\" src=\"https:\/\/pressbooks.ccconline.org\/acccomposition1\/wp-content\/uploads\/sites\/83\/2022\/08\/CNX_Stats_C05_M01_item002-1.jpg\" alt=\"This graph slopes downward. It begins at a point on the y-axis and approaches the x-axis at the right edge of the graph.\" width=\"380\" data-media-type=\"image\/jpg\" \/><\/span><\/div>\n<\/div>\n<\/div>\n<div id=\"eip-idm137825120\" data-type=\"exercise\">\n<div id=\"eip-idm143442320\" data-type=\"problem\">\n<p id=\"eip-idm143442064\">Which type of distribution does the graph illustrate?<\/p>\n<div id=\"eip-idm143441680\" class=\"bc-figure figure\"><span id=\"eip-idp45343472\" data-type=\"media\" data-alt=\"This graph shows a bell-shaped graph. The symmetric graph reaches maximum height at x = 0 and slopes downward gradually to the x-axis on each side of the peak.\"><img decoding=\"async\" src=\"https:\/\/pressbooks.ccconline.org\/acccomposition1\/wp-content\/uploads\/sites\/83\/2022\/08\/CNX_Stats_C05_M01_item003-1.jpg\" alt=\"This graph shows a bell-shaped graph. The symmetric graph reaches maximum height at x = 0 and slopes downward gradually to the x-axis on each side of the peak.\" width=\"380\" data-media-type=\"image\/jpg\" \/><\/span><\/div>\n<\/div>\n<div id=\"eip-idm191766752\" data-type=\"solution\">\n<p id=\"eip-idm70312624\">Normal Distribution<\/p>\n<\/div>\n<\/div>\n<div id=\"eip-idm170433264\" data-type=\"exercise\">\n<div id=\"eip-idm170433008\" data-type=\"problem\">\n<p id=\"eip-idm170432752\">What does the shaded area represent? <em data-effect=\"italics\">P<\/em>(___&lt; <em data-effect=\"italics\">x<\/em> &lt; ___)<\/p>\n<div id=\"eip-idp7874608\" class=\"bc-figure figure\"><span id=\"eip-idm79769968\" data-type=\"media\" data-alt=\"This graph shows a uniform distribution. The horizontal axis ranges from 0 to 10. The distribution is modeled by a rectangle extending from x = 1 to x = 8. A region from x = 2 to x = 5 is shaded inside the rectangle.\"><img decoding=\"async\" src=\"https:\/\/pressbooks.ccconline.org\/acccomposition1\/wp-content\/uploads\/sites\/83\/2022\/08\/CNX_Stats_C05_M01_item004-1.jpg\" alt=\"This graph shows a uniform distribution. The horizontal axis ranges from 0 to 10. The distribution is modeled by a rectangle extending from x = 1 to x = 8. A region from x = 2 to x = 5 is shaded inside the rectangle.\" width=\"380\" data-media-type=\"image\/jpg\" \/><\/span><\/div>\n<\/div>\n<\/div>\n<div id=\"eip-idm160222016\" data-type=\"exercise\">\n<div id=\"eip-idm40131600\" data-type=\"problem\">\n<p id=\"eip-idm40131344\">What does the shaded area represent? <em data-effect=\"italics\">P<\/em>(___&lt; <em data-effect=\"italics\">x<\/em> &lt; ___)<\/p>\n<div id=\"eip-idm126372688\" class=\"bc-figure figure\"><span id=\"eip-idm126372432\" data-type=\"media\" data-alt=\"This graph shows an exponential distribution. The graph slopes downward. It begins at a point on the y-axis and approaches the x-axis at the right edge of the graph. The region under the graph from x = 6 to x = 7 is shaded.\"><img decoding=\"async\" src=\"https:\/\/pressbooks.ccconline.org\/acccomposition1\/wp-content\/uploads\/sites\/83\/2022\/08\/CNX_Stats_C05_M01_item005-1.jpg\" alt=\"This graph shows an exponential distribution. The graph slopes downward. It begins at a point on the y-axis and approaches the x-axis at the right edge of the graph. The region under the graph from x = 6 to x = 7 is shaded.\" width=\"380\" data-media-type=\"image\/jpg\" \/><\/span><\/div>\n<\/div>\n<div id=\"eip-idm164759504\" data-type=\"solution\">\n<p id=\"eip-idm59247088\"><em data-effect=\"italics\">P<\/em>(6 &lt; <em data-effect=\"italics\">x<\/em> &lt; 7)<\/p>\n<\/div>\n<\/div>\n<div id=\"fs-idm118866416\" data-type=\"exercise\">\n<div id=\"fs-idm94113008\" data-type=\"problem\">\n<p id=\"fs-idm186932672\">For a continuous probablity distribution, 0 \u2264 <em data-effect=\"italics\">x<\/em> \u2264 15. What is <em data-effect=\"italics\">P<\/em>(<em data-effect=\"italics\">x<\/em> &gt; 15)?<\/p>\n<\/div>\n<\/div>\n<div id=\"fs-idm154014752\" data-type=\"exercise\">\n<div id=\"fs-idm158384896\" data-type=\"problem\">\n<p id=\"fs-idm174567168\">What is the area under <em data-effect=\"italics\">f<\/em>(<em data-effect=\"italics\">x<\/em>) if the function is a continuous probability density function?<\/p>\n<\/div>\n<div id=\"fs-idm96621808\" data-type=\"solution\">\n<p id=\"fs-idm101963728\">one<\/p>\n<\/div>\n<\/div>\n<div id=\"fs-idm159828512\" data-type=\"exercise\">\n<div id=\"fs-idm28635392\" data-type=\"problem\">\n<p id=\"fs-idm44266992\">For a continuous probability distribution, 0 \u2264 <em data-effect=\"italics\">x<\/em> \u2264 10. What is <em data-effect=\"italics\">P<\/em>(<em data-effect=\"italics\">x<\/em> = 7)?<\/p>\n<\/div>\n<\/div>\n<div id=\"fs-idm89415120\" data-type=\"exercise\">\n<div id=\"fs-idm119661456\" data-type=\"problem\">\n<p id=\"fs-idm114444880\">A <strong>continuous<\/strong> probability function is restricted to the portion between <em data-effect=\"italics\">x<\/em> = 0 and 7. What is <em data-effect=\"italics\">P<\/em>(<em data-effect=\"italics\">x<\/em> = 10)?<\/p>\n<\/div>\n<div id=\"fs-idm29287760\" data-type=\"solution\">\n<p id=\"fs-idm160336672\">zero<\/p>\n<\/div>\n<\/div>\n<div id=\"fs-idm185391792\" data-type=\"exercise\">\n<div id=\"fs-idm70578720\" data-type=\"problem\">\n<p id=\"fs-idm83804704\"><em data-effect=\"italics\">f<\/em>(<em data-effect=\"italics\">x<\/em>) for a continuous probability function is \\(\\frac{1}{5}\\), and the function is restricted to 0 \u2264 <em data-effect=\"italics\">x<\/em> \u2264 5. What is <em data-effect=\"italics\">P<\/em>(<em data-effect=\"italics\">x<\/em> &lt; 0)?<\/p>\n<\/div>\n<\/div>\n<div id=\"fs-idm78277152\" data-type=\"exercise\">\n<div id=\"fs-idm119655680\" data-type=\"problem\">\n<p id=\"fs-idm107695264\"><em data-effect=\"italics\">f<\/em>(<em data-effect=\"italics\">x<\/em>), a continuous probability function, is equal to \\(\\frac{1}{12}\\), and the function is restricted to 0 \u2264 <em data-effect=\"italics\">x<\/em> \u2264 12. What is <em data-effect=\"italics\">P<\/em> (0 &lt; <em data-effect=\"italics\">x<\/em> &lt; 12)?<\/p>\n<\/div>\n<div id=\"fs-idm109882608\" data-type=\"solution\">\n<p id=\"fs-idm185543600\">one<\/p>\n<\/div>\n<\/div>\n<div id=\"fs-idm31115936\" data-type=\"exercise\">\n<div id=\"fs-idm126442096\" data-type=\"problem\">\n<p id=\"fs-idm79659008\">Find the probability that <em data-effect=\"italics\">x<\/em> falls in the shaded area.<\/p>\n<div id=\"fs-idm29576816\" class=\"bc-figure figure\"><span id=\"fs-idm168532640\" data-type=\"media\" data-alt=\"\"><img decoding=\"async\" src=\"https:\/\/pressbooks.ccconline.org\/acccomposition1\/wp-content\/uploads\/sites\/83\/2022\/08\/CNX_Stats_C05_M02_item001-1.jpg\" alt=\"\" width=\"380\" data-media-type=\"image\/jpg\" \/><\/span><\/div>\n<\/div>\n<\/div>\n<div id=\"fs-idm29257104\" data-type=\"exercise\">\n<div id=\"fs-idm70564992\" data-type=\"problem\">\n<p id=\"fs-idm5797792\">Find the probability that <em data-effect=\"italics\">x<\/em> falls in the shaded area.<\/p>\n<div id=\"fs-idm120132416\" class=\"bc-figure figure\"><span id=\"fs-idm17039824\" data-type=\"media\" data-alt=\"\"><img decoding=\"async\" src=\"https:\/\/pressbooks.ccconline.org\/acccomposition1\/wp-content\/uploads\/sites\/83\/2022\/08\/CNX_Stats_C05_M02_item002-1.jpg\" alt=\"\" width=\"380\" data-media-type=\"image\/jpg\" \/><\/span><\/div>\n<\/div>\n<div id=\"fs-idm192509264\" data-type=\"solution\">\n<p id=\"fs-idm100002320\">0.625<\/p>\n<\/div>\n<\/div>\n<div id=\"fs-idm144329792\" data-type=\"exercise\">\n<div id=\"fs-idm109804912\" data-type=\"problem\">\n<p id=\"fs-idp1777728\">Find the probability that <em data-effect=\"italics\">x<\/em> falls in the shaded area.<\/p>\n<div id=\"fs-idm167436128\" class=\"bc-figure figure\"><span id=\"fs-idm163441712\" data-type=\"media\" data-alt=\"\"><img decoding=\"async\" src=\"https:\/\/pressbooks.ccconline.org\/acccomposition1\/wp-content\/uploads\/sites\/83\/2022\/08\/CNX_Stats_C05_M02_item003-1.jpg\" alt=\"\" width=\"380\" data-media-type=\"image\/jpg\" \/><\/span><\/div>\n<\/div>\n<\/div>\n<div id=\"fs-idm170928704\" data-type=\"exercise\">\n<div id=\"fs-idm76313888\" data-type=\"problem\">\n<p id=\"fs-idm73539776\"><em data-effect=\"italics\">f<\/em>(<em data-effect=\"italics\">x<\/em>), a continuous probability function, is equal to \\(\\frac{1}{3}\\) and the function is restricted to 1 \u2264 <em data-effect=\"italics\">x<\/em> \u2264 4. Describe \\(P\\left(x&gt;\\frac{3}{2}\\right).\\)<\/p>\n<\/div>\n<div id=\"fs-idm63500944\" data-type=\"solution\">\n<p id=\"fs-idm21180864\">The probability is equal to the area from <em data-effect=\"italics\">x<\/em> = \\(\\frac{3}{2}\\) to <em data-effect=\"italics\">x<\/em> = 4 above the x-axis and up to <em data-effect=\"italics\">f<\/em>(<em data-effect=\"italics\">x<\/em>) = \\(\\frac{1}{3}\\).<\/p>\n<\/div>\n<\/div>\n<\/div>\n<div id=\"fs-idp5416000\" class=\"free-response\" data-depth=\"1\">\n<h3 data-type=\"title\">Homework<\/h3>\n<p id=\"eip-idm57931200\"><em data-effect=\"italics\">For each probability and percentile problem, draw the picture.<\/em><\/p>\n<div id=\"eip-idp84147744\" data-type=\"exercise\">\n<div id=\"eip-idp84148000\" data-type=\"problem\">\n<p id=\"eip-idp36661712\">1) <span style=\"font-size: 1em\">When age is rounded to the nearest year, do the data stay continuous, or do they become discrete? \u00a0Why?<\/span><\/p>\n<\/div>\n<\/div>\n<div id=\"eip-idm16922624\" data-type=\"exercise\">\n<div id=\"eip-idm19380464\" data-type=\"solution\">\n<p>2) Consider the following experiment. You are one of 100 people enlisted to take part in a study to determine the percent of nurses in America with an R.N. (registered nurse) degree. \u00a0You ask nurses if they have an R.N. degree. \u00a0The nurses answer \u201cyes\u201d or \u201cno.\u201d \u00a0You then calculate the percentage of nurses with an R.N. degree. \u00a0You give that percentage to your supervisor.<\/p>\n<ol id=\"eip-idp36662096\" type=\"a\">\n<li>What part of the experiment will yield discrete data?<\/li>\n<li>What part of the experiment will yield continuous data?<\/li>\n<\/ol>\n<p><strong>Answers to odd questions<\/strong><\/p>\n<p>1) Age is a measurement, regardless of the accuracy used.<\/p>\n<\/div>\n<\/div>\n<\/div>\n","protected":false},"author":32,"menu_order":36,"template":"","meta":{"pb_show_title":"","pb_short_title":"","pb_subtitle":"","pb_authors":[],"pb_section_license":""},"chapter-type":[],"contributor":[],"license":[],"class_list":["post-210","chapter","type-chapter","status-publish","hentry"],"part":188,"_links":{"self":[{"href":"https:\/\/pressbooks.ccconline.org\/accintrostats\/wp-json\/pressbooks\/v2\/chapters\/210","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/pressbooks.ccconline.org\/accintrostats\/wp-json\/pressbooks\/v2\/chapters"}],"about":[{"href":"https:\/\/pressbooks.ccconline.org\/accintrostats\/wp-json\/wp\/v2\/types\/chapter"}],"author":[{"embeddable":true,"href":"https:\/\/pressbooks.ccconline.org\/accintrostats\/wp-json\/wp\/v2\/users\/32"}],"version-history":[{"count":2,"href":"https:\/\/pressbooks.ccconline.org\/accintrostats\/wp-json\/pressbooks\/v2\/chapters\/210\/revisions"}],"predecessor-version":[{"id":621,"href":"https:\/\/pressbooks.ccconline.org\/accintrostats\/wp-json\/pressbooks\/v2\/chapters\/210\/revisions\/621"}],"part":[{"href":"https:\/\/pressbooks.ccconline.org\/accintrostats\/wp-json\/pressbooks\/v2\/parts\/188"}],"metadata":[{"href":"https:\/\/pressbooks.ccconline.org\/accintrostats\/wp-json\/pressbooks\/v2\/chapters\/210\/metadata\/"}],"wp:attachment":[{"href":"https:\/\/pressbooks.ccconline.org\/accintrostats\/wp-json\/wp\/v2\/media?parent=210"}],"wp:term":[{"taxonomy":"chapter-type","embeddable":true,"href":"https:\/\/pressbooks.ccconline.org\/accintrostats\/wp-json\/pressbooks\/v2\/chapter-type?post=210"},{"taxonomy":"contributor","embeddable":true,"href":"https:\/\/pressbooks.ccconline.org\/accintrostats\/wp-json\/wp\/v2\/contributor?post=210"},{"taxonomy":"license","embeddable":true,"href":"https:\/\/pressbooks.ccconline.org\/accintrostats\/wp-json\/wp\/v2\/license?post=210"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}