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According to the National Institute on Alcohol Abuse and Alcoholism (NIAAA), and

ID: 3371704 • Letter: A

Question

According to the National Institute on Alcohol Abuse and Alcoholism (NIAAA), and the National Institutes of Health (NIH), 41% of college students nationwide engage in “binge drinking” behavior, having five or more drinks on one occasion during the past two weeks. A college president wonders if the proportion of students enrolled at her college that binge drink is lower than the national proportion. In a commissioned study, 462 students are selected randomly from a list of all students enrolled at the college. Of these, 162 admitted to having engaged in binge drinking. Using your estimate for , what sample size would be required to reduce the margin of error to 2 percentage points? 2017 2187 2401 4802

Explanation / Answer

Sol:

estimate=sample proportion=p^=x/n=162/462=0.3506

1-p^=1-0.3506=0.6494

Z crit for 5%=1.96

E=0.02

WE HAVE

n=p^*q^(Zalpha/2/E)^2

=0.3506*0.6494*(1.96/0.02)^2

=2186.6

=2187

OPTION B

2187

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