{"id":76,"date":"2019-06-18T12:51:34","date_gmt":"2019-06-18T16:51:34","guid":{"rendered":"https:\/\/pressbooks.library.torontomu.ca\/pohmath\/chapter\/probability\/"},"modified":"2023-11-27T14:19:25","modified_gmt":"2023-11-27T19:19:25","slug":"probability","status":"publish","type":"chapter","link":"https:\/\/pressbooks.library.torontomu.ca\/pohmath\/chapter\/probability\/","title":{"raw":"6.1. Sample Spaces and Probability","rendered":"6.1. Sample Spaces and Probability"},"content":{"raw":"<div>[Latexpage]<\/div>\n<h1><strong>Sample Spaces and Probability<\/strong><\/h1>\nIf two coins are tossed, what is the probability that both coins will fall heads? The problem seems simple enough, but it is not uncommon to hear the incorrect answer of $1\/3$. A student may incorrectly reason that if two coins are tossed there are three possibilities, one head, two heads, or no heads. Therefore, the probability of two heads is one out of three. The answer is wrong because if we toss two coins there are four possibilities and not three. For clarity, assume that one coin is a penny and the other a nickel. Then we have the following four possibilities:\n<p style=\"text-align: center\">HH HT TH TT<\/p>\nThe possibility HT, for example, indicates a head on the penny and a tail on the nickel, while TH represents a tail on the penny and a head on the nickel.\n\nIt is for this reason, we emphasize the need for understanding sample spaces.\n\nAn act of flipping coins, rolling dice, drawing cards, or surveying people are referred to as an <strong>experiment<\/strong>.\n\n&nbsp;\n<div class=\"textbox shaded\"><strong>Sample Spaces<\/strong>: A sample space of an experiment is the set of all possible outcomes.<\/div>\n&nbsp;\n<div class=\"textbox textbox--examples\"><header class=\"textbox__header\">\n<p class=\"textbox__title\">Example 6.1.1<\/p>\n\n<\/header>\n<div class=\"textbox__content\">If a die is rolled, write a sample space.<\/div>\n<div class=\"textbox__content\"><strong>Solution <\/strong><\/div>\n<div class=\"textbox__content\">A die has six faces each having an equally likely chance of appearing. Therefore, the set of all possible outcomes <strong>S<\/strong> is:<\/div>\n<div class=\"textbox__content\" style=\"text-align: center\">{1, 2, 3, 4, 5, 6}.<\/div>\n<\/div>\n&nbsp;\n<div class=\"textbox textbox--examples\"><header class=\"textbox__header\">\n<p class=\"textbox__title\">Example 6.1.2<\/p>\n\n<\/header>\n<div class=\"textbox__content\">A family has three children. Write a sample space.<\/div>\n<div class=\"textbox__content\"><strong>Solution <\/strong><\/div>\n<div class=\"textbox__content\">The sample space consists of eight possibilities:<\/div>\n<div class=\"textbox__content\" style=\"text-align: center\">{BBB , BBG , BGB , BGG , GBB , GBG , GGB , GGG}<\/div>\n<div class=\"textbox__content\">The possibility BGB, for example, indicates that the first born is a boy, the second born a girl, and the third a boy.<\/div>\n<div class=\"textbox__content\">\n\nWe illustrate these possibilities with a tree diagram:\n<div class=\"textbox\">\\begin{tikzpicture}[grow=right,-&gt;,&gt;=angle 60]\n\\tikzstyle{level 1}=[level distance=20mm, sibling distance=50mm]\n\\tikzstyle{level 2}=[level distance=20mm, sibling distance=20mm]\n\\tikzstyle{level 3}=[level distance=25mm, sibling distance=10mm]\n%\\begin{scope}[yshift=0]\n\\node (0) {}\nchild {node {$G$}\nchild {node {$G$}\nchild {node {$G\\quad GGG$}\n}\nchild {node {$B\\quad GGB$}\n}\n}\nchild {node {$B$}\nchild {node {$G\\quad GBG$}\n}\nchild {node {$B\\quad GBB$}\n}\n}\n}\nchild {node{$B$}\nchild {node{$G$}\nchild {node {$G\\quad BGG$}\n}\nchild {node {$B\\quad BGB$}\n}\n}\nchild {node{$B$}\nchild {node {$G\\quad BBG$}\n}\nchild {node {$B\\quad BBB$}\n}\n}\n};\n%\\end{scope}\n\\end{tikzpicture}<\/div>\n<\/div>\n<\/div>\n&nbsp;\n<div class=\"textbox textbox--examples\"><header class=\"textbox__header\">\n<p class=\"textbox__title\">Example 6.1.3<\/p>\n\n<\/header>\n<div class=\"textbox__content\">Two dice are rolled. Write the sample space.<\/div>\n<div class=\"textbox__content\"><strong>Solution <\/strong><\/div>\n<div class=\"textbox__content\">\n\nWe assume one of the dice is red, and the other green. We have the following 36 possibilities:\n<table style=\"border-collapse: collapse;width: 100%\" border=\"0\">\n<tbody>\n<tr>\n<td class=\"border\" style=\"width: 14.2857%;text-align: center\"><\/td>\n<td class=\"border\" style=\"width: 85.7142%;text-align: center\" colspan=\"6\">Green<\/td>\n<\/tr>\n<tr>\n<td class=\"border\" style=\"width: 14.2857%;text-align: center\">Red<\/td>\n<td class=\"border\" style=\"width: 14.2857%;text-align: center\">1<\/td>\n<td class=\"border\" style=\"width: 14.2857%;text-align: center\">2<\/td>\n<td class=\"border\" style=\"width: 14.2857%;text-align: center\">3<\/td>\n<td class=\"border\" style=\"width: 14.2857%;text-align: center\">4<\/td>\n<td class=\"border\" style=\"width: 14.2857%;text-align: center\">5<\/td>\n<td class=\"border\" style=\"width: 14.2857%;text-align: center\">6<\/td>\n<\/tr>\n<tr>\n<td class=\"border\" style=\"width: 14.2857%;text-align: center\">1<\/td>\n<td class=\"border\" style=\"width: 14.2857%;text-align: center\">(1, 1)<\/td>\n<td class=\"border\" style=\"width: 14.2857%;text-align: center\">(1, 2)<\/td>\n<td class=\"border\" style=\"width: 14.2857%;text-align: center\">(1, 3)<\/td>\n<td class=\"border\" style=\"width: 14.2857%;text-align: center\">(1, 4)<\/td>\n<td class=\"border\" style=\"width: 14.2857%;text-align: center\">(1, 5)<\/td>\n<td class=\"border\" style=\"width: 14.2857%;text-align: center\">(1, 6)<\/td>\n<\/tr>\n<tr>\n<td class=\"border\" style=\"width: 14.2857%;text-align: center\">2<\/td>\n<td class=\"border\" style=\"width: 14.2857%;text-align: center\">(2, 1)<\/td>\n<td class=\"border\" style=\"width: 14.2857%;text-align: center\">(2, 2)<\/td>\n<td class=\"border\" style=\"width: 14.2857%;text-align: center\">(2, 3)<\/td>\n<td class=\"border\" style=\"width: 14.2857%;text-align: center\">(2, 4)<\/td>\n<td class=\"border\" style=\"width: 14.2857%;text-align: center\">(2, 5)<\/td>\n<td class=\"border\" style=\"width: 14.2857%;text-align: center\">(2, 6)<\/td>\n<\/tr>\n<tr>\n<td class=\"border\" style=\"width: 14.2857%;text-align: center\">3<\/td>\n<td class=\"border\" style=\"width: 14.2857%;text-align: center\">(3, 1)<\/td>\n<td class=\"border\" style=\"width: 14.2857%;text-align: center\">(3, 2)<\/td>\n<td class=\"border\" style=\"width: 14.2857%;text-align: center\">(3, 3)<\/td>\n<td class=\"border\" style=\"width: 14.2857%;text-align: center\">(3, 4)<\/td>\n<td class=\"border\" style=\"width: 14.2857%;text-align: center\">(3, 5)<\/td>\n<td class=\"border\" style=\"width: 14.2857%;text-align: center\">(3, 6)<\/td>\n<\/tr>\n<tr>\n<td class=\"border\" style=\"width: 14.2857%;text-align: center\">4<\/td>\n<td class=\"border\" style=\"width: 14.2857%;text-align: center\">(4, 1)<\/td>\n<td class=\"border\" style=\"width: 14.2857%;text-align: center\">(4, 2)<\/td>\n<td class=\"border\" style=\"width: 14.2857%;text-align: center\">(4, 3)<\/td>\n<td class=\"border\" style=\"width: 14.2857%;text-align: center\">(4, 4)<\/td>\n<td class=\"border\" style=\"width: 14.2857%;text-align: center\">(4, 5)<\/td>\n<td class=\"border\" style=\"width: 14.2857%;text-align: center\">(4, 6)<\/td>\n<\/tr>\n<tr>\n<td class=\"border\" style=\"width: 14.2857%;text-align: center\">5<\/td>\n<td class=\"border\" style=\"width: 14.2857%;text-align: center\">(5, 1)<\/td>\n<td class=\"border\" style=\"width: 14.2857%;text-align: center\">(5, 2)<\/td>\n<td class=\"border\" style=\"width: 14.2857%;text-align: center\">(5, 3)<\/td>\n<td class=\"border\" style=\"width: 14.2857%;text-align: center\">(5, 4)<\/td>\n<td class=\"border\" style=\"width: 14.2857%;text-align: center\">(5, 5)<\/td>\n<td class=\"border\" style=\"width: 14.2857%;text-align: center\">(5, 6)<\/td>\n<\/tr>\n<tr>\n<td class=\"border\" style=\"width: 14.2857%;text-align: center\">6<\/td>\n<td class=\"border\" style=\"width: 14.2857%;text-align: center\">(6, 1)<\/td>\n<td class=\"border\" style=\"width: 14.2857%;text-align: center\">(6, 2)<\/td>\n<td class=\"border\" style=\"width: 14.2857%;text-align: center\">(6, 3)<\/td>\n<td class=\"border\" style=\"width: 14.2857%;text-align: center\">(6, 4)<\/td>\n<td class=\"border\" style=\"width: 14.2857%;text-align: center\">(6, 5)<\/td>\n<td class=\"border\" style=\"width: 14.2857%;text-align: center\">(6, 6)<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n<div class=\"textbox__content\">The entry (2, 5), for example, indicates that the red die shows a two, and the green a 5.<\/div>\n<\/div>\n&nbsp;\n\nNow that we understand the concept of a sample space, we will define probability.\n<div class=\"textbox shaded\">\n\n<strong>Probability<\/strong>: For a sample space <em>S<\/em>, and an outcome <em>A<\/em> of <em>S<\/em>, the following two properties are satisfied.\n<ol>\n \t<li>If <em>A<\/em> is an outcome of a sample space, then the probability of <em>A<\/em>, denoted by <em>P<\/em>(<em>A<\/em>), is between 0 and 1, inclusive.\u00a0 \u00a0 \u00a00 \u2264 <em style=\"font-size: 1rem\">P<\/em><span style=\"font-size: 1rem\">(<\/span><em style=\"font-size: 1rem\">A<\/em><span style=\"font-size: 1rem\">) \u2264 1<\/span><\/li>\n \t<li>The sum of the probabilities of all the outcomes in <em style=\"font-size: 1rem\">S<\/em><span style=\"font-size: 1rem\"> equals 1.<\/span><\/li>\n<\/ol>\n<\/div>\n&nbsp;\n<div class=\"textbox textbox--examples\"><header class=\"textbox__header\">\n<p class=\"textbox__title\">Example 6.1.4<\/p>\n\n<\/header>\n<div class=\"textbox__content\">If two dice, one red and one green, are rolled, find the probability that the red die shows a 3 and the green shows a six.<\/div>\n<div class=\"textbox__content\"><strong>Solution <\/strong><\/div>\n<div class=\"textbox__content\">Since two dice are rolled, there are 36 possibilities. The probability of each outcome, listed in Example 6.1.3, is equally likely. Since (3, 6) is one such outcome, the probability of obtaining (3, 6) is 1\/36.<\/div>\n<\/div>\n&nbsp;\n\nThe example we just considered consisted of only one outcome of the sample space. We are often interested in finding probabilities of several outcomes represented by an event.\n\nAn <strong>event<\/strong> is a subset of a sample space. If an event consists of only one outcome, it is called a <strong>simple event<\/strong>.\n\n&nbsp;\n<div class=\"textbox textbox--examples\"><header class=\"textbox__header\">\n<p class=\"textbox__title\">Example 6.1.5<\/p>\n\n<\/header>\n<div class=\"textbox__content\">If two dice are rolled, find the probability that the sum of the faces of the dice is 7.<\/div>\n<div class=\"textbox__content\"><strong>Solution <\/strong><\/div>\n<div class=\"textbox__content\">Let <em>E<\/em> represent the event that the sum of the faces of two dice is 7. Since the possible cases for the sum to be 7 are: (1, 6), (2, 5), (3, 4), (4, 3), (5, 2), and (6, 1).<\/div>\n<div class=\"textbox__content\" style=\"text-align: center\"><em>E<\/em> = {(1, 6), (2, 5), (3, 4), (4, 3), (5, 2), and (6, 1)}<\/div>\n<div class=\"textbox__content\">and the probability of the event E:<\/div>\n<div class=\"textbox__content\" style=\"text-align: center\"><em>P<\/em>(<em>E<\/em>) = 6\/36 or 1\/6.<\/div>\n<\/div>\n&nbsp;\n<div class=\"textbox textbox--examples\"><header class=\"textbox__header\">\n<p class=\"textbox__title\">Example 6.1.6<\/p>\n\n<\/header>\n<div class=\"textbox__content\">A jar contains 3 red, 4 white, and 3 blue marbles. If a marble is chosen at random, what is the probability that the marble is a red marble or a blue marble?<\/div>\n<div class=\"textbox__content\"><strong>Solution <\/strong><\/div>\n<div class=\"textbox__content\">We assume the marbles are <em>r<\/em><sub>1<\/sub>, <em>r<\/em><sub>2<\/sub>, <em>r<\/em><sub>3<\/sub>, <em>w<\/em><sub>1<\/sub>, <em>w<\/em><sub>2<\/sub>, <em>w<\/em><sub>3<\/sub>, <em>w<\/em><sub>4<\/sub>, <em>b<\/em><sub>1<\/sub>, <em>b<\/em><sub>2<\/sub>, <em>b<\/em><sub>3<\/sub>. Let the event <em>C<\/em> represent that the marble is red or blue.<\/div>\n<div class=\"textbox__content\">The sample space <em>S<\/em> = {<em>r<\/em><sub>1<\/sub>, <em>r<\/em><sub>2<\/sub>, <em>r<\/em><sub>3<\/sub>, <em>w<\/em><sub>1<\/sub>, <em>w<\/em><sub>2<\/sub>, <em>w<\/em><sub>3<\/sub>, <em>w<\/em><sub>4<\/sub>, <em>b<\/em><sub>1<\/sub>, <em>b<\/em><sub>2<\/sub>, <em>b<\/em><sub>3<\/sub>}<\/div>\n<div class=\"textbox__content\">And the event <em>C<\/em> = {<em>r<\/em><sub>1<\/sub>, <em>r<\/em><sub>2<\/sub>, <em>r<\/em><sub>3<\/sub>, <em>b<\/em><sub>1<\/sub>, <em>b<\/em><sub>2<\/sub>, <em>b<\/em><sub>3<\/sub>}<\/div>\n<div class=\"textbox__content\">Therefore, the probability of <em>C:<\/em><\/div>\n<div class=\"textbox__content\" style=\"text-align: center\"><em>P<\/em>(<em>C<\/em>) = 6\/10 or 3\/5.<\/div>\n<\/div>\n&nbsp;\n<div class=\"textbox textbox--examples\"><header class=\"textbox__header\">\n<p class=\"textbox__title\">Example 6.1.7<\/p>\n\n<\/header>\n<div class=\"textbox__content\">A jar contains three marbles numbered 1, 2, and 3. If two marbles are drawn, what is the probability that the sum of the numbers is 4?<\/div>\n<div class=\"textbox__content\"><strong>Solution <\/strong><\/div>\n<div class=\"textbox__content\">Since two marbles are drawn, the sample space consists of the following six possibilities:<\/div>\n<div class=\"textbox__content\" style=\"text-align: center\">S = {(1, 2), (1, 3), (2, 3), (2, 1), (3, 1), (3, 2)}<\/div>\n<div class=\"textbox__content\">Let the event <em>F<\/em> represent that the sum of the numbers is four. Then:<\/div>\n<div class=\"textbox__content\" style=\"text-align: center\">F = [(1, 3), (3, 1)]<\/div>\n<div class=\"textbox__content\">Therefore, the probability of F is:<\/div>\n<div class=\"textbox__content\" style=\"text-align: center\"><em>P<\/em>(<em>F<\/em>) = 2\/6 or 1\/3.<\/div>\n<\/div>\n&nbsp;\n<div class=\"textbox textbox--examples\"><header class=\"textbox__header\">\n<p class=\"textbox__title\">Example 6.1.8<\/p>\n\n<\/header>\n<div class=\"textbox__content\">A jar contains three marbles numbered 1, 2, and 3. If two marbles are drawn, what is the probability that the sum of the numbers is <em>at least<\/em> 4?<\/div>\n<div class=\"textbox__content\"><strong>Solution<\/strong><\/div>\n<div class=\"textbox__content\">The sample space, as in Example 6.1.7, consists of the following six possibilities:<\/div>\n<div class=\"textbox__content\" style=\"text-align: center\"><em>S<\/em> = {(1, 2), (1, 3), (2, 3), (2, 1), (3, 1), (3, 2)}<\/div>\n<div class=\"textbox__content\">Let the event <em>A<\/em> represent that the sum of the numbers is at least four. Then:<\/div>\n<div class=\"textbox__content\" style=\"text-align: center\"><em>F<\/em> = {(1, 3), (3, 1), (2, 3), (3, 2)}<\/div>\n<div class=\"textbox__content\">Therefore, the probability of <em>F<\/em> is:<\/div>\n<div class=\"textbox__content\" style=\"text-align: center\"><em>P<\/em>(<em>F<\/em>) = 4\/6 or 2\/3.<\/div>\n<\/div>\n&nbsp;\n<h1><strong>Practice questions<\/strong><\/h1>\n<strong>1.<\/strong> Write a sample space for the following event: a die is rolled, and a coin is tossed.\n\n<strong>2. <\/strong>A card is selected from a deck of 52 playing cards. Find the following probabilities:\n<p style=\"padding-left: 40px\"><strong>a<\/strong>.\u00a0<em>P<\/em> (a king)<\/p>\n<p style=\"padding-left: 40px\"><b>b.<\/b> <em>P<\/em> (any suit other than hearts)<\/p>\n<strong>3. <\/strong>A\u00a0jar contains 6 red, 7 white, and 7 blue marbles. If a marble is chosen at random, find the following probabilities:\n<p style=\"padding-left: 40px\"><strong>a<\/strong>.\u00a0<em>P<\/em> (red)<\/p>\n<p style=\"padding-left: 40px\"><b>b.<\/b> <em>P<\/em> (red or blue)<\/p>\n<strong>4. <\/strong>Two dice are rolled. Find the following probabilities:\n<p style=\"padding-left: 40px\"><strong>a<\/strong>.\u00a0<em>P<\/em> (the sum of the dice is 5)<\/p>\n<p style=\"padding-left: 40px\"><b>b.<\/b> <em>P<\/em> (the sum of the dice is 3 or 6)<\/p>\n<strong>5. <\/strong>A family has four children. Find the following probabilities:\n<p style=\"padding-left: 40px\"><strong>a<\/strong>.\u00a0<em>P<\/em> (they have two boys and two girls)<\/p>\n<p style=\"padding-left: 40px\"><b>b.<\/b> <em>P<\/em> (they have three or more girls)<\/p>\n&nbsp;","rendered":"<div><\/div>\n<h1><strong>Sample Spaces and Probability<\/strong><\/h1>\n<p>If two coins are tossed, what is the probability that both coins will fall heads? The problem seems simple enough, but it is not uncommon to hear the incorrect answer of <img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/pressbooks.library.torontomu.ca\/pohmath\/wp-content\/ql-cache\/quicklatex.com-70fe1cb9414497311c99c05dd6897f17_l3.png\" class=\"ql-img-inline-formula quicklatex-auto-format\" alt=\"&#49;&#47;&#51;\" title=\"Rendered by QuickLaTeX.com\" height=\"19\" width=\"26\" style=\"vertical-align: -5px;\" \/>. A student may incorrectly reason that if two coins are tossed there are three possibilities, one head, two heads, or no heads. Therefore, the probability of two heads is one out of three. The answer is wrong because if we toss two coins there are four possibilities and not three. For clarity, assume that one coin is a penny and the other a nickel. Then we have the following four possibilities:<\/p>\n<p style=\"text-align: center\">HH HT TH TT<\/p>\n<p>The possibility HT, for example, indicates a head on the penny and a tail on the nickel, while TH represents a tail on the penny and a head on the nickel.<\/p>\n<p>It is for this reason, we emphasize the need for understanding sample spaces.<\/p>\n<p>An act of flipping coins, rolling dice, drawing cards, or surveying people are referred to as an <strong>experiment<\/strong>.<\/p>\n<p>&nbsp;<\/p>\n<div class=\"textbox shaded\"><strong>Sample Spaces<\/strong>: A sample space of an experiment is the set of all possible outcomes.<\/div>\n<p>&nbsp;<\/p>\n<div class=\"textbox textbox--examples\">\n<header class=\"textbox__header\">\n<p class=\"textbox__title\">Example 6.1.1<\/p>\n<\/header>\n<div class=\"textbox__content\">If a die is rolled, write a sample space.<\/div>\n<div class=\"textbox__content\"><strong>Solution <\/strong><\/div>\n<div class=\"textbox__content\">A die has six faces each having an equally likely chance of appearing. Therefore, the set of all possible outcomes <strong>S<\/strong> is:<\/div>\n<div class=\"textbox__content\" style=\"text-align: center\">{1, 2, 3, 4, 5, 6}.<\/div>\n<\/div>\n<p>&nbsp;<\/p>\n<div class=\"textbox textbox--examples\">\n<header class=\"textbox__header\">\n<p class=\"textbox__title\">Example 6.1.2<\/p>\n<\/header>\n<div class=\"textbox__content\">A family has three children. Write a sample space.<\/div>\n<div class=\"textbox__content\"><strong>Solution <\/strong><\/div>\n<div class=\"textbox__content\">The sample space consists of eight possibilities:<\/div>\n<div class=\"textbox__content\" style=\"text-align: center\">{BBB , BBG , BGB , BGG , GBB , GBG , GGB , GGG}<\/div>\n<div class=\"textbox__content\">The possibility BGB, for example, indicates that the first born is a boy, the second born a girl, and the third a boy.<\/div>\n<div class=\"textbox__content\">\n<p>We illustrate these possibilities with a tree diagram:<\/p>\n<div class=\"textbox\">\n<p class=\"ql-center-picture\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/pressbooks.library.torontomu.ca\/pohmath\/wp-content\/ql-cache\/quicklatex.com-2ff677c51d0e50cf3349c1b9c867a4c4_l3.png\" height=\"381\" width=\"331\" class=\"ql-img-picture quicklatex-auto-format\" alt=\"Rendered by QuickLaTeX.com\" title=\"Rendered by QuickLaTeX.com\" \/><\/p>\n<\/div>\n<\/div>\n<\/div>\n<p>&nbsp;<\/p>\n<div class=\"textbox textbox--examples\">\n<header class=\"textbox__header\">\n<p class=\"textbox__title\">Example 6.1.3<\/p>\n<\/header>\n<div class=\"textbox__content\">Two dice are rolled. Write the sample space.<\/div>\n<div class=\"textbox__content\"><strong>Solution <\/strong><\/div>\n<div class=\"textbox__content\">\n<p>We assume one of the dice is red, and the other green. We have the following 36 possibilities:<\/p>\n<table style=\"border-collapse: collapse;width: 100%\">\n<tbody>\n<tr>\n<td class=\"border\" style=\"width: 14.2857%;text-align: center\"><\/td>\n<td class=\"border\" style=\"width: 85.7142%;text-align: center\" colspan=\"6\">Green<\/td>\n<\/tr>\n<tr>\n<td class=\"border\" style=\"width: 14.2857%;text-align: center\">Red<\/td>\n<td class=\"border\" style=\"width: 14.2857%;text-align: center\">1<\/td>\n<td class=\"border\" style=\"width: 14.2857%;text-align: center\">2<\/td>\n<td class=\"border\" style=\"width: 14.2857%;text-align: center\">3<\/td>\n<td class=\"border\" style=\"width: 14.2857%;text-align: center\">4<\/td>\n<td class=\"border\" style=\"width: 14.2857%;text-align: center\">5<\/td>\n<td class=\"border\" style=\"width: 14.2857%;text-align: center\">6<\/td>\n<\/tr>\n<tr>\n<td class=\"border\" style=\"width: 14.2857%;text-align: center\">1<\/td>\n<td class=\"border\" style=\"width: 14.2857%;text-align: center\">(1, 1)<\/td>\n<td class=\"border\" style=\"width: 14.2857%;text-align: center\">(1, 2)<\/td>\n<td class=\"border\" style=\"width: 14.2857%;text-align: center\">(1, 3)<\/td>\n<td class=\"border\" style=\"width: 14.2857%;text-align: center\">(1, 4)<\/td>\n<td class=\"border\" style=\"width: 14.2857%;text-align: center\">(1, 5)<\/td>\n<td class=\"border\" style=\"width: 14.2857%;text-align: center\">(1, 6)<\/td>\n<\/tr>\n<tr>\n<td class=\"border\" style=\"width: 14.2857%;text-align: center\">2<\/td>\n<td class=\"border\" style=\"width: 14.2857%;text-align: center\">(2, 1)<\/td>\n<td class=\"border\" style=\"width: 14.2857%;text-align: center\">(2, 2)<\/td>\n<td class=\"border\" style=\"width: 14.2857%;text-align: center\">(2, 3)<\/td>\n<td class=\"border\" style=\"width: 14.2857%;text-align: center\">(2, 4)<\/td>\n<td class=\"border\" style=\"width: 14.2857%;text-align: center\">(2, 5)<\/td>\n<td class=\"border\" style=\"width: 14.2857%;text-align: center\">(2, 6)<\/td>\n<\/tr>\n<tr>\n<td class=\"border\" style=\"width: 14.2857%;text-align: center\">3<\/td>\n<td class=\"border\" style=\"width: 14.2857%;text-align: center\">(3, 1)<\/td>\n<td class=\"border\" style=\"width: 14.2857%;text-align: center\">(3, 2)<\/td>\n<td class=\"border\" style=\"width: 14.2857%;text-align: center\">(3, 3)<\/td>\n<td class=\"border\" style=\"width: 14.2857%;text-align: center\">(3, 4)<\/td>\n<td class=\"border\" style=\"width: 14.2857%;text-align: center\">(3, 5)<\/td>\n<td class=\"border\" style=\"width: 14.2857%;text-align: center\">(3, 6)<\/td>\n<\/tr>\n<tr>\n<td class=\"border\" style=\"width: 14.2857%;text-align: center\">4<\/td>\n<td class=\"border\" style=\"width: 14.2857%;text-align: center\">(4, 1)<\/td>\n<td class=\"border\" style=\"width: 14.2857%;text-align: center\">(4, 2)<\/td>\n<td class=\"border\" style=\"width: 14.2857%;text-align: center\">(4, 3)<\/td>\n<td class=\"border\" style=\"width: 14.2857%;text-align: center\">(4, 4)<\/td>\n<td class=\"border\" style=\"width: 14.2857%;text-align: center\">(4, 5)<\/td>\n<td class=\"border\" style=\"width: 14.2857%;text-align: center\">(4, 6)<\/td>\n<\/tr>\n<tr>\n<td class=\"border\" style=\"width: 14.2857%;text-align: center\">5<\/td>\n<td class=\"border\" style=\"width: 14.2857%;text-align: center\">(5, 1)<\/td>\n<td class=\"border\" style=\"width: 14.2857%;text-align: center\">(5, 2)<\/td>\n<td class=\"border\" style=\"width: 14.2857%;text-align: center\">(5, 3)<\/td>\n<td class=\"border\" style=\"width: 14.2857%;text-align: center\">(5, 4)<\/td>\n<td class=\"border\" style=\"width: 14.2857%;text-align: center\">(5, 5)<\/td>\n<td class=\"border\" style=\"width: 14.2857%;text-align: center\">(5, 6)<\/td>\n<\/tr>\n<tr>\n<td class=\"border\" style=\"width: 14.2857%;text-align: center\">6<\/td>\n<td class=\"border\" style=\"width: 14.2857%;text-align: center\">(6, 1)<\/td>\n<td class=\"border\" style=\"width: 14.2857%;text-align: center\">(6, 2)<\/td>\n<td class=\"border\" style=\"width: 14.2857%;text-align: center\">(6, 3)<\/td>\n<td class=\"border\" style=\"width: 14.2857%;text-align: center\">(6, 4)<\/td>\n<td class=\"border\" style=\"width: 14.2857%;text-align: center\">(6, 5)<\/td>\n<td class=\"border\" style=\"width: 14.2857%;text-align: center\">(6, 6)<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n<div class=\"textbox__content\">The entry (2, 5), for example, indicates that the red die shows a two, and the green a 5.<\/div>\n<\/div>\n<p>&nbsp;<\/p>\n<p>Now that we understand the concept of a sample space, we will define probability.<\/p>\n<div class=\"textbox shaded\">\n<p><strong>Probability<\/strong>: For a sample space <em>S<\/em>, and an outcome <em>A<\/em> of <em>S<\/em>, the following two properties are satisfied.<\/p>\n<ol>\n<li>If <em>A<\/em> is an outcome of a sample space, then the probability of <em>A<\/em>, denoted by <em>P<\/em>(<em>A<\/em>), is between 0 and 1, inclusive.\u00a0 \u00a0 \u00a00 \u2264 <em style=\"font-size: 1rem\">P<\/em><span style=\"font-size: 1rem\">(<\/span><em style=\"font-size: 1rem\">A<\/em><span style=\"font-size: 1rem\">) \u2264 1<\/span><\/li>\n<li>The sum of the probabilities of all the outcomes in <em style=\"font-size: 1rem\">S<\/em><span style=\"font-size: 1rem\"> equals 1.<\/span><\/li>\n<\/ol>\n<\/div>\n<p>&nbsp;<\/p>\n<div class=\"textbox textbox--examples\">\n<header class=\"textbox__header\">\n<p class=\"textbox__title\">Example 6.1.4<\/p>\n<\/header>\n<div class=\"textbox__content\">If two dice, one red and one green, are rolled, find the probability that the red die shows a 3 and the green shows a six.<\/div>\n<div class=\"textbox__content\"><strong>Solution <\/strong><\/div>\n<div class=\"textbox__content\">Since two dice are rolled, there are 36 possibilities. The probability of each outcome, listed in Example 6.1.3, is equally likely. Since (3, 6) is one such outcome, the probability of obtaining (3, 6) is 1\/36.<\/div>\n<\/div>\n<p>&nbsp;<\/p>\n<p>The example we just considered consisted of only one outcome of the sample space. We are often interested in finding probabilities of several outcomes represented by an event.<\/p>\n<p>An <strong>event<\/strong> is a subset of a sample space. If an event consists of only one outcome, it is called a <strong>simple event<\/strong>.<\/p>\n<p>&nbsp;<\/p>\n<div class=\"textbox textbox--examples\">\n<header class=\"textbox__header\">\n<p class=\"textbox__title\">Example 6.1.5<\/p>\n<\/header>\n<div class=\"textbox__content\">If two dice are rolled, find the probability that the sum of the faces of the dice is 7.<\/div>\n<div class=\"textbox__content\"><strong>Solution <\/strong><\/div>\n<div class=\"textbox__content\">Let <em>E<\/em> represent the event that the sum of the faces of two dice is 7. Since the possible cases for the sum to be 7 are: (1, 6), (2, 5), (3, 4), (4, 3), (5, 2), and (6, 1).<\/div>\n<div class=\"textbox__content\" style=\"text-align: center\"><em>E<\/em> = {(1, 6), (2, 5), (3, 4), (4, 3), (5, 2), and (6, 1)}<\/div>\n<div class=\"textbox__content\">and the probability of the event E:<\/div>\n<div class=\"textbox__content\" style=\"text-align: center\"><em>P<\/em>(<em>E<\/em>) = 6\/36 or 1\/6.<\/div>\n<\/div>\n<p>&nbsp;<\/p>\n<div class=\"textbox textbox--examples\">\n<header class=\"textbox__header\">\n<p class=\"textbox__title\">Example 6.1.6<\/p>\n<\/header>\n<div class=\"textbox__content\">A jar contains 3 red, 4 white, and 3 blue marbles. If a marble is chosen at random, what is the probability that the marble is a red marble or a blue marble?<\/div>\n<div class=\"textbox__content\"><strong>Solution <\/strong><\/div>\n<div class=\"textbox__content\">We assume the marbles are <em>r<\/em><sub>1<\/sub>, <em>r<\/em><sub>2<\/sub>, <em>r<\/em><sub>3<\/sub>, <em>w<\/em><sub>1<\/sub>, <em>w<\/em><sub>2<\/sub>, <em>w<\/em><sub>3<\/sub>, <em>w<\/em><sub>4<\/sub>, <em>b<\/em><sub>1<\/sub>, <em>b<\/em><sub>2<\/sub>, <em>b<\/em><sub>3<\/sub>. Let the event <em>C<\/em> represent that the marble is red or blue.<\/div>\n<div class=\"textbox__content\">The sample space <em>S<\/em> = {<em>r<\/em><sub>1<\/sub>, <em>r<\/em><sub>2<\/sub>, <em>r<\/em><sub>3<\/sub>, <em>w<\/em><sub>1<\/sub>, <em>w<\/em><sub>2<\/sub>, <em>w<\/em><sub>3<\/sub>, <em>w<\/em><sub>4<\/sub>, <em>b<\/em><sub>1<\/sub>, <em>b<\/em><sub>2<\/sub>, <em>b<\/em><sub>3<\/sub>}<\/div>\n<div class=\"textbox__content\">And the event <em>C<\/em> = {<em>r<\/em><sub>1<\/sub>, <em>r<\/em><sub>2<\/sub>, <em>r<\/em><sub>3<\/sub>, <em>b<\/em><sub>1<\/sub>, <em>b<\/em><sub>2<\/sub>, <em>b<\/em><sub>3<\/sub>}<\/div>\n<div class=\"textbox__content\">Therefore, the probability of <em>C:<\/em><\/div>\n<div class=\"textbox__content\" style=\"text-align: center\"><em>P<\/em>(<em>C<\/em>) = 6\/10 or 3\/5.<\/div>\n<\/div>\n<p>&nbsp;<\/p>\n<div class=\"textbox textbox--examples\">\n<header class=\"textbox__header\">\n<p class=\"textbox__title\">Example 6.1.7<\/p>\n<\/header>\n<div class=\"textbox__content\">A jar contains three marbles numbered 1, 2, and 3. If two marbles are drawn, what is the probability that the sum of the numbers is 4?<\/div>\n<div class=\"textbox__content\"><strong>Solution <\/strong><\/div>\n<div class=\"textbox__content\">Since two marbles are drawn, the sample space consists of the following six possibilities:<\/div>\n<div class=\"textbox__content\" style=\"text-align: center\">S = {(1, 2), (1, 3), (2, 3), (2, 1), (3, 1), (3, 2)}<\/div>\n<div class=\"textbox__content\">Let the event <em>F<\/em> represent that the sum of the numbers is four. Then:<\/div>\n<div class=\"textbox__content\" style=\"text-align: center\">F = [(1, 3), (3, 1)]<\/div>\n<div class=\"textbox__content\">Therefore, the probability of F is:<\/div>\n<div class=\"textbox__content\" style=\"text-align: center\"><em>P<\/em>(<em>F<\/em>) = 2\/6 or 1\/3.<\/div>\n<\/div>\n<p>&nbsp;<\/p>\n<div class=\"textbox textbox--examples\">\n<header class=\"textbox__header\">\n<p class=\"textbox__title\">Example 6.1.8<\/p>\n<\/header>\n<div class=\"textbox__content\">A jar contains three marbles numbered 1, 2, and 3. If two marbles are drawn, what is the probability that the sum of the numbers is <em>at least<\/em> 4?<\/div>\n<div class=\"textbox__content\"><strong>Solution<\/strong><\/div>\n<div class=\"textbox__content\">The sample space, as in Example 6.1.7, consists of the following six possibilities:<\/div>\n<div class=\"textbox__content\" style=\"text-align: center\"><em>S<\/em> = {(1, 2), (1, 3), (2, 3), (2, 1), (3, 1), (3, 2)}<\/div>\n<div class=\"textbox__content\">Let the event <em>A<\/em> represent that the sum of the numbers is at least four. Then:<\/div>\n<div class=\"textbox__content\" style=\"text-align: center\"><em>F<\/em> = {(1, 3), (3, 1), (2, 3), (3, 2)}<\/div>\n<div class=\"textbox__content\">Therefore, the probability of <em>F<\/em> is:<\/div>\n<div class=\"textbox__content\" style=\"text-align: center\"><em>P<\/em>(<em>F<\/em>) = 4\/6 or 2\/3.<\/div>\n<\/div>\n<p>&nbsp;<\/p>\n<h1><strong>Practice questions<\/strong><\/h1>\n<p><strong>1.<\/strong> Write a sample space for the following event: a die is rolled, and a coin is tossed.<\/p>\n<p><strong>2. <\/strong>A card is selected from a deck of 52 playing cards. Find the following probabilities:<\/p>\n<p style=\"padding-left: 40px\"><strong>a<\/strong>.\u00a0<em>P<\/em> (a king)<\/p>\n<p style=\"padding-left: 40px\"><b>b.<\/b> <em>P<\/em> (any suit other than hearts)<\/p>\n<p><strong>3. <\/strong>A\u00a0jar contains 6 red, 7 white, and 7 blue marbles. If a marble is chosen at random, find the following probabilities:<\/p>\n<p style=\"padding-left: 40px\"><strong>a<\/strong>.\u00a0<em>P<\/em> (red)<\/p>\n<p style=\"padding-left: 40px\"><b>b.<\/b> <em>P<\/em> (red or blue)<\/p>\n<p><strong>4. <\/strong>Two dice are rolled. Find the following probabilities:<\/p>\n<p style=\"padding-left: 40px\"><strong>a<\/strong>.\u00a0<em>P<\/em> (the sum of the dice is 5)<\/p>\n<p style=\"padding-left: 40px\"><b>b.<\/b> <em>P<\/em> (the sum of the dice is 3 or 6)<\/p>\n<p><strong>5. <\/strong>A family has four children. Find the following probabilities:<\/p>\n<p style=\"padding-left: 40px\"><strong>a<\/strong>.\u00a0<em>P<\/em> (they have two boys and two girls)<\/p>\n<p style=\"padding-left: 40px\"><b>b.<\/b> <em>P<\/em> (they have three or more girls)<\/p>\n<p>&nbsp;<\/p>\n","protected":false},"author":2,"menu_order":1,"template":"","meta":{"pb_show_title":"","pb_short_title":"","pb_subtitle":"","pb_authors":[],"pb_section_license":""},"chapter-type":[49],"contributor":[],"license":[],"class_list":["post-76","chapter","type-chapter","status-publish","hentry","chapter-type-numberless"],"part":75,"_links":{"self":[{"href":"https:\/\/pressbooks.library.torontomu.ca\/pohmath\/wp-json\/pressbooks\/v2\/chapters\/76","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/pressbooks.library.torontomu.ca\/pohmath\/wp-json\/pressbooks\/v2\/chapters"}],"about":[{"href":"https:\/\/pressbooks.library.torontomu.ca\/pohmath\/wp-json\/wp\/v2\/types\/chapter"}],"author":[{"embeddable":true,"href":"https:\/\/pressbooks.library.torontomu.ca\/pohmath\/wp-json\/wp\/v2\/users\/2"}],"version-history":[{"count":2,"href":"https:\/\/pressbooks.library.torontomu.ca\/pohmath\/wp-json\/pressbooks\/v2\/chapters\/76\/revisions"}],"predecessor-version":[{"id":190,"href":"https:\/\/pressbooks.library.torontomu.ca\/pohmath\/wp-json\/pressbooks\/v2\/chapters\/76\/revisions\/190"}],"part":[{"href":"https:\/\/pressbooks.library.torontomu.ca\/pohmath\/wp-json\/pressbooks\/v2\/parts\/75"}],"metadata":[{"href":"https:\/\/pressbooks.library.torontomu.ca\/pohmath\/wp-json\/pressbooks\/v2\/chapters\/76\/metadata\/"}],"wp:attachment":[{"href":"https:\/\/pressbooks.library.torontomu.ca\/pohmath\/wp-json\/wp\/v2\/media?parent=76"}],"wp:term":[{"taxonomy":"chapter-type","embeddable":true,"href":"https:\/\/pressbooks.library.torontomu.ca\/pohmath\/wp-json\/pressbooks\/v2\/chapter-type?post=76"},{"taxonomy":"contributor","embeddable":true,"href":"https:\/\/pressbooks.library.torontomu.ca\/pohmath\/wp-json\/wp\/v2\/contributor?post=76"},{"taxonomy":"license","embeddable":true,"href":"https:\/\/pressbooks.library.torontomu.ca\/pohmath\/wp-json\/wp\/v2\/license?post=76"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}