Based on a survey of nearly all of the ninth- and twelfth-graders in Minnesota p
ID: 3300477 • Letter: B
Question
Based on a survey of nearly all of the ninth- and twelfth-graders in Minnesota public schools in 1998, a total of 78,564 students, Stinchfield (2001) reported proportions admitting that they had gambled at least once a week during the previous year. He found that these proportions differed considerably for males and females, as well as for ninth- and twelfth-graders. One result he found was that 22.9% of the ninth-grade boys but only 4.5% of the ninth-grade girls admitted gambling at least weekly. The probability that a randomly selected ninth grader is a boy is 0.491. A tree diagram for this scenario (without the last branch probabilities) is shown below. Use this information for the following two questions.
Use the tree diagram to find the probability that a randomly selected ninth-grader is a girl and is a weekly gambler.
______
Use the tree diagram to find the probability that a randomly selected ninth-grader is a weekly gambler. Show your work.
________
Weekly gambler? Yes Sex .229 Boy 491 509 Yes 045 Girl 955 NoExplanation / Answer
A) P(girl is a weekly gambler) = 0.509 * 0.045 = 0.0229
B) P(weekly gambler) = P(boy and weekly gambler) + P(girl and weekly gambler) = 0.491 * 0.229 + 0.509 * 0.045 = 0.1353
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