# EBook Problems Infer 2Proportions

## EBook Problems Set - Inferences about Two Proportions Problems

### Problem 1

A random sample of 1000 Americans aged 65 and older was collected in 1980 and found that 15% had "hazardous" levels of drinking, which is defined as regularly drinking an amount of alcohol that could cause health problems given the subject's medical conditions. Researchers wanted to know if this proportion has changed since 1980 and so collected a random sample of 1500 Americans aged 65 and older in 2004. They found that 12% drank at hazardous levels. Which of the following is closest to the value of a test statistic that could be used to test the hypothesis that the proportion of hazardous drinkers over the age of 65 has declined since 1980?

- Choose one answer.

*(a) -2.13*

*(b) 0.014*

*(c) 0.418*

*(d) 4.54*

### Problem 2

A marketing director for a radio station collects a random sample of three hundred 18 to 25 year-olds and two hundred and fifty 25 to 40 year-olds. She records the percent of each group that had purchased music online in the last 30 days. She performs a hypothesis test, and the p-value of her test turns out to be 0.15. From this she should conclude:

- Choose one answer.

*(a) there is insufficient evidence to conclude that there is a difference in the proportion of on-line music purchases in the younger and older group.*

*(b) that about 15% more people purchased on-line music in the younger group than in the older group.*

*(c) the proportion of on-line music purchasers is the same in the under-25 year-old group as in the older group.*

*(d) the probability of getting the same results again is .15.*

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