Ch 9-11 Flashcards
changing from a 95% confidence interval estimate for a population proportion to a 99% confidence interval estimate, with all other things being equal
- increases the interval size by 4%
- decreases the interval size by 4%
- increases the interval size by 31%
- decreases the interval size by 31%
- this question cannot be answered without knowing the sample size
increases the interval size by 315
in general, how does doubling the sample size change the confidence interval size?
- doubles the interval size
- halves the interval size
- multiplies the interval size by 1.414
- divides the interval size by 1.414
- this question cannot be answered without knowing the sample size
divides the interval size 1.414
a confidence interval estimate is determined from the GPA of a simple random sample of n students. All other things being equal, which of the following will result in a smaller margin of error?
i. a smaller confidence level
ii. a smaller sample standard deviation
iii. a smaller sample size
i and ii
a sample was conducted to determine the percentage of high school students who planned to go to college. The results were stated as 82% with a margin of error of 5%. What is meant by 5%?
- five percent of the population not surveyed
- in the sample, the percentage of students who plan to go to college was between 77% and 87%
- the percentage of the entire population of students who plan to go to college is between 77% and 87%
- it is unlikely that the given sample proportion result would be obtained unless the true percentage was between 77% and 87%
- between 77% and 87% of the population were surveyed
it is unlikely the given sample proportion result would be obtained unless the true percentage was between 77% and 87%
one month the actual unemployment rate in France was 13.4%. If during that month you took an SRS of 100 Frenchman and constructed a confidence interval estimate of the unemployment rate, which of the following would have been true?
i. the center of the interval was 13.4
ii. the interval contained 13.4
iii. a 99% confidence interval estimate contained 13.4
none of the above gives the complete set of true responses
the margin of error in a confidence interval estimate using z-scores covers which of the following?
i. random sampling errors
ii. errors due to over-coverage and nonresponse in obtaining sample surveys
iii. errors due to using sample standard deviations as estimates for population standard deviations
i only
A USA Today “Lifeline” column reported that in a survey of 500 people, 39% said they watch their bread while it’s being toasted. Establish a 90% confidence interval estimate for the percentage of people who watch their bread being toasted.
- 39% + .0785%
- 39% + 2.2%
- 39% + 2.8%
- 39% + 3.6%
- 39% + 4.3%
39% + 3.6%
In a survey funded by Burroughs-Welcome, 750 of 1000 adult Americans said they didn’t believe they could come down with an STD. Construct a 95% confidence interval estimate of the proportion of adult Americans who don’t believe they can contract an STD.
(.723, .777)
A 1993 Los Angeles Times poll of 1703 adults revealed that only 17% thought the media was doing a “very good” job. With what degree of confidence can the newspaper job say that 17% + 2% of adults believe the media is doing a “very good” job?
- 72.9%
- 90%
- 95%
- 97.2%
- 98.6%
97.2%
A politician wants to know what percentage of the voters support her position on the issue of forced busing for integration. What size voter sample should be obtained to determine with 90% confidence the support level to within 4%?
- 21
- 25
- 423
- 600
- 1691
423
In a 1994 New York Times poll measuring a candidate’s popularity, the newspaper claimed that in 19 of 20 cases, its poll results should be no more than 3 percentage points off in either direction. What confidence level are the pollsters working with, and what size sample should they have obtained?
- 3%, 20
- 6%, 20
- 6%, 100
- 95%, 33
- 95%, 1068
95%
1068
The National Research Council of the Philippines reported that 210 of 361 members in biology are women, but only 34 of 86 members in mathematics are women. Establish a 95% confidence interval estimate of the difference in proportions of women in biology and women in mathematics in the Philippines.
.187 + .115
In a simple random sample of 300 elderly men, 65% were married, while in an independent simple random sample of 400 elderly women, 48% were married. Determine a 99% confidence interval estimate for the difference between the percentages of elderly men and women who are married.
17% + 9.6%
A researcher plans to investigate the difference between the proportion of psychiatrists and the proportion of psychologists who believe that most emotional problems have their root cause in childhood. How large a sample should be taken to be 90% certain of knowing the difference to within 3%
- 39
- 376
- 752
- 1504
- 3007
752
Which of the following are true statements?
i. the p-value of a test is the probability of obtaining a result as extreme as the one obtained assuming the null hypothesis is true
ii. if the p-value for a test is 0.15, the probability that the null hypothesis is true is .015
iii. when the null hypothesis is rejected, it is because it is not true
none of the above fives the complete set of true responses
