### Question 15.10

The Bureau of Labor Statistics announces that last month it interviewed all members of the labor force in a sample of 60,000 households; 7.8% of the people interviewed were unemployed. The boldface number is a

• (a) sampling distribution.
• (b) statistic.
• (c) parameter.

### Question 15.11

A study of voting chose 663 registered Canadian voters at random shortly after the 2011 elections. Of these, 69% said they had voted in the election. Election records show that only 61.4% of registered voters voted in the election, up from 59.1% in 2008. The boldface number is a

• (a) sampling distribution.
• (b) statistic.
• (c) parameter.

### Question 15.12

A 2011 study finds that in a random sample of 3000 American adults aged 18 to 34, 2140 owned an MP3 player such as an iPod. The sample proportion who own an MP3 player is

• (a) 71.
• (b) 0.67.
• (c) 0.71.

### Question 15.13

In the previous exercise, the sample proportion is an unbiased estimator of the proportion p of all American adults aged 18 to 34 who own an MP3 player. Unbiasedness in this situation means that

• (a) in many samples from this population, the mean of the many values of will be equal to p.
• (b) as we take larger and larger samples from this population, will get closer and closer to p.
• (c) in many samples from this population, the many values of will have a distribution that is close to Normal.

### Question 15.14

The proportion of drivers who use seat belts depends on things like age, sex, and ethnicity. As part of a broader study, investigators observed a random sample of 117 female Hispanic drivers in Boston. Suppose that in fact 60% of all female Hispanic drivers in the Boston area wear seat belts. In repeated samples, the sample proportion would follow approximately a Normal distribution with mean

• (a) 70.2.
• (b) 0.6.
• (c) 0.4.

### Question 15.15

The standard deviation of the distribution of in the previous exercise is about

• (a) 0.002.
• (b) 0.045.
• (c) 0.24.

### Question 15.16

Low birthweight is the second-leading cause of infant mortality in the United States. A newborn baby has low birth weight if it weighs less than 2500 grams, with approximately 8% of infants born at a low birthweight. A sample of 500 babies is selected. The approximate distribution of , the proportion of low birth weight infants in the sample, is

• (a) N(8, 0.074).
• (b) N(0.8, 0.012).
• (c) N(0.08, 0.012).

### Question 15.17

In the previous exercise, the probability that more than 45 infants in the sample are born at a low birthweight is approximately

• (a) 0.82.
• (b) 0.20.
• (c) 0.18.