Theme IV Inference Review

Theme IV Inference Review

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Multiple Choice

Changing from 95% confidence interval estimate for a population proportion to a 99% confidence interval estimate, with all other things being equal, will

• Increase the interval size

• Decrease the interval size

• Increase the sample size

• Cannot be done

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Multiple Choice

In general, how does doubling the sample size change the confidence interval size?

• The interval gets bigger

• The interval stays the same

• The interval gets smaller

• Cannot be determined

Multiple Choice

A confidence interval estimate is determined from the GPAs of a simple random sample of n students. 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

• I and III

• II and III

• I, II and III

Multiple Choice

A survey 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 5%. What is meant by 5%?

• Five percent of the entire population were 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%.

Multiple Choice

One month the actual unemployment rate in France was 13.4%. If during that month you took an SRS of 100 Frenchmen and constructed a confidence interval estimate of the unemployment rate, which of the following would be true?

I. The center of the interval was 13.4.

II. The interval contained 13.4.

A 99% confidence interval estimate contained 13.4.

• I and II

• I and III

• I, II, and III

• None of the above gives the complete set of true responses

Poll

How are you feeling so far about the test tomorrow?

Multiple Choice

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 undercoverage and nonresponse in obtaining sample surveys

III. Errors due to using sample standard deviations as estimates for population standard deviations

• I only

• II only

• III only

• I and II

Multiple Choice

Two 90% confidence interval estimates are obtained:

I (28.5, 34.5) and II (30.3, 38.2).

a. If the sample sizes are the same, which has the larger standard deviation?

b. If the sample standard deviations are the same, which has the larger size?

• a. I b. I

• a. I b. II

• a.II b. I

• a. II b. II

Multiple Choice

Suppose (25, 30) is a 90% confidence interval estimate for a population mean . Which of the following are true statements?

I. There is a .90 probability that is between 25 and 30.

II. If 100 random samples of the given size are picked and a 90% confidence interval estimates is calculated from each, then will be in 90 of the resulting intervals.

III. If 90% confidence intervals are calculated from all possible samples of the given size, will be in 90% of these intervals.

• I only

• II only

• III only

• None of the above

Multiple Choice

The time that it takes an untrained rat to run a standard maze has a Normal distribution with mean 65 seconds and standard deviation 15 seconds. The researchers want to use a test of hypotheses to determine whether training significantly improves the rats' completion times. An appropriate alternative hypothesis would have the form

• H_a: μ > 65

• H_a: x bar < 65

• H_a: μ < 65

• H_a: x bar > 65

Multiple Choice

A researcher collects infant mortality data from a random sample of villages in a certain country. It is claimed that the average death rate in this country is the same as that of a neighboring country, which is known to be 17 deaths per 1000 live births. To test this claim using a test of hypotheses, what should the null and alternative hypotheses be?

• H₀: μ = 17

  H_a: μ ≠ 17

• H₀: μ ≠ 17

  H_a: μ = 17

• H₀: μ = 17

  H_a: μ > 17

• H₀: x bar = 17

  H_a: x bar ≠ 17

Multiple Choice

Which of the following P-values obtained from a test of hypotheses constitutes the least amount of evidence against the null hypothesis?

• 0.107

• 0.207

• 0.017

• 0.007

Multiple Choice

Suppose we conduct a test of hypotheses and find that the test results are significant at level = 0.025. Which of the following statements then must be true?

• The results are significant at level = 0.05

• The results are significant at level = 0.02

• The results are significant at level = 0.01

• The test results are important

Multiple Choice

The Department of Health plans to test the lead level in a public park. The park will be closed if the lead level exceeds the allowed limit. Otherwise, the park will be kept open. The department conducts the test using soil samples gathered at randomly selected locations. Which of the following decisions would constitute making a Type I error in this situation?

• keeping the park open when the average lead level exceeds the allowed limit

• closing the park when the average lead level is acceptable

• closing the park when the average lead level exceeds the allowed limit

• keeping the park open so Hereford seniors can meet up to hang out

Poll

Are you ready for a 10 question multiple choice/drag and drop test tomorrow?