Download Chapter 9 Multiple Choice Practice 8. You want to estimate the

Chapter 9 Multiple Choice Practice
8. You want to estimate the proportion of undergraduates at a college who favor eliminating
evening exams. You will choose an SRS. If you enlarge your SRS from 250 to 1000 students, the
sample proportion p̂
(a) will have the same mean and the same standard deviation.
(b) will have smaller bias and the standard deviation will be 1/4 as large.
(c) will have smaller bias and the standard deviation will be 1/2 as large.
(d) will have the same mean and the standard deviation will be 1/4 as large.
(e) will have the same mean and the standard deviation will be 1/2 as large.
9. The phrase "95% confidence" in a Gallup Poll press release means that
(a) our results are true for 95% of the population of all adults.
(b) 95% of the population falls within the margin of error we announce.
(c) the probability is 0.95 that a randomly chosen adult falls in the margin of error we announce.
(d) we got these results using a method that gives correct answers in 95% of all samples.
10. A recent Gallup Poll interviewed a random sample of 1523 adults. Of these, 868 bought a
lottery ticket in the past year. A 95% confidence interval for the proportion of all adults who
bought a lottery ticket in the past year is (assume Gallup used an SRS)
(a) 0.57  0.00016
(b) 0.57  0.00032
(c) 0.57  0.013
(d) 0.57  0.025
(e) 0.57  0.03
11. Suppose that in fact (unknown to Gallup) exactly 60% of all adults bought a lottery ticket in
the past year. If Gallup took many SRSs of 1523 people, the sample proportion who bought a
ticket would vary from sample to sample. The sampling distribution would be close to normal
with
(a) mean 0.6 and standard deviation 0.00016
(b) mean 0.6 and standard deviation 0.0126
(c) mean 0.6 and standard deviation 0.4899
(d) mean 0.6 and standard deviation 0.0251
12. The same Gallup Poll asked its 1523 adult respondents and also 501 teens (ages 13 to 17)
whether they generally approved of legal gambling: 63% of adults and 52% of teens said yes.
The margin of error for a 95% confidence statement about teens would be
(a) greater than for adults, because the teen sample is smaller.
(b) less than for adults, because the teen sample is smaller.
(c) less than for adults, because there are fewer teens in the population.
(d) the same as for adults, because they both come from the same sample survey.
(e) can't say, because it depends on what percent of each population was in the sample.
A shocking fact: 66% of all teenagers have a TV set in their room. If an opinion poll chooses an
SRS of 1000 teens and asks if they have a TV set in their room, the percent who say "Yes" will
vary if the sample is repeated. In fact, the percent "Yes" in many samples will follow a normal
distribution with mean 66% and standard deviation 1.5%. The next three questions concern this
fact.
13. Which of these ranges of outcomes contains 95% of all the results of a large number of polls
of 1000 teens?
(a) 66% to 100%
(b) 64.5% to 67.5%
(c) 63% to 69%
(d) 61.5% to 70.5%
14. Although the result will vary if the poll is repeated, the distribution of results is centered at
the truth about the population (66%). We call this desirable property of an SRS
(a) lack of bias.
(b) low variability.
(c) symmetry.
(d) margin of error.
15. The variation from sample to sample when the poll is repeated is described by the standard
deviation (1.5%). We would like this variation to be small, so that repeated polls give almost the
same result. To reduce the standard deviation, we could
(a) use an SRS of size less than 1000.
(b) use an SRS of size greater than 1000.
(c) use a confidence level less than 95%.
(d) use a confidence level greater than 95%.
(e) Both (b) and (c).
16. If the value of the standardized test statistic z is 2.5,
(a) conclude that the null hypothesis and the alternative hypothesis are the same
(b) we reject the null hypothesis at the 5% significance level
(c) we fail to reject the null hypothesis at the 5% significance level
(d) we reject the alternative hypothesis at the 5% significance level
(e) should use a different null hypothesis
17. The null hypothesis is
(a) another name for the alternative hypothesis
(b) true with 95% probability
(c) usually a statement of "no effect" or "no difference"
(d) determined by looking at the data
(e) statistically significant
18. If a significance test gives a P-value of 0.50,
(a) the margin of error is 0.50
(b) the null hypothesis is very likely to be true
(c) we do not have good evidence against the null hypothesis
(d) we do have good evidence against the null hypothesis
(e) the effect of interest is practically significant
19. We observe p̂ = 0.3. If the standard deviation of the sampling distribution of p̂ is 0.04,
what is the 95% confidence interval for p?
(a) 0.26 to 0.34
(b) 0.18 to 0.42
(c) 0.3 plus or minus 0.08
(d) 0.04 plus or minus 0.6
(e) 99% accurate
In March, 2000, the New York Times conducted "a telephone poll of a random sample of 1003
adults in all 50 states, giving all phone numbers, listed and unlisted, a proportionate chance of
being included." We can treat this as a simple random sample. One question asked was, "Do you
think what is shown on television today is less moral than American society, more moral than
American society, or accurately reflects morality in American society?" Of the answers, 46%
said "Less," 37% said "Accurate," 9% said "More," and the others had no opinion. The next six
questions concern this sample survey.
37. The population for the poll is
(a) the 1003 people interviewed.
(b) a simple random sample.
(c) the 46% who think TV is less moral than society.
(d) all adults living in the United States.
38. The number 46% is
(a) a parameter because it describes the population.
(b) a parameter because it describes the sample.
(c) a statistic because it describes the population.
(d) a statistic because it describes the sample.
39. If the poll were repeated at the same time using the same sampling method, the percent who
think TV is less moral than society
(a) would be 46%, because the same method will give the same result.
(b) would be less than 46% because of bias.
(c) could be either greater or less than 46%, because of chance variation in random sampling.
(d) could be either greater or less than 46%, because of bias.
40. A 95% confidence interval for the percent of all adults who think TV is less moral than
society is about
41. We might use these data to answer the question, "Do more than half of all adults think TV is
less moral than society?" To do this, we would take as our null hypothesis
42. The P-value for the test in the previous question is about 0.99. This means that
(a) the poll gives very strong evidence that more than half of adults feel TV is less moral than
society.
(b) the poll gives weak evidence that more than half of adults feel TV is less moral than society.
(c) the poll sheds no light on whether more than half of adults feel TV is less moral than society.
(d) the poll gives no evidence that more than half of adults feel TV is less moral than society.