If a difference seen in sample results is statistically significant it means that
a. there is an important difference in the sample results.
b. there is an important difference in the population.
c. the difference observed in the sample was unlikely to have occurred if there is no difference in the population.
d. there is an important difference in the population that wasn't reflected in the sample results.
Q. 2Does Prayer Lower Blood Pressure was a question asked in Case Study 1.5 . The moral of the story was
a. cause-and-effect conclusions can generally be made in an observational study.
b. cause-and-effect conclusions cannot generally be made in an observational study.
c. cause-and-effect conclusions can generally be made in an experiment.
d. cause-and-effect conclusions cannot generally be made in an experiment.
Q. 3In the study described in Case Study 1.4, questionnaires were sent to 100,000 women asking about love, sex and relationships. Only 4.5 of the women responded. This means that
a. the margin of error for the survey was 4.5.
b. a random sample was not contacted.
c. women who felt strongly did not respond.
d. nonresponse bias was likely to be a major problem.
Q. 4If a magazine sends a survey to a random sample of 10,000 of its subscribers but only 3000 of them return the survey, the sample results may not be representative of the population of subscribers because
a. they used a self-selected sample.
b. there is likely to be nonresponse bias.
c. a volunteer sample was used.
d. they used a random sample.
Q. 5Suppose a Gallup Poll using a sample of 400 individuals found that 25 of them supported a particular opinion. An interval that is 95 certain to contain the truth about the population percent who support that opinion is
a. 25 0.05 or 24.95 to 25.05.
b. 25 0.25 or 24.75 to 25.25.
c. 25 5 or 20 to 30.
d. 25 20 or 5 to 45.
Q. 6Which of the following is true about the margin of error for the most common types of surveys?
a. If the number of individuals in the sample were to be substantially increased, the margin of error would decrease.
b. If the number of individuals in the sample were to be substantially decreased, the margin of error would also decrease.
c. If the number of individuals in the sample were to be substantially increased, the margin of error would not change.
d. If the number of individuals in the sample were to be substantially decreased, the margin of error would not change.
Q. 7Which of the following is true about the use of sample surveys?
a. Everyone in the population must also be in the sample.
b. Data from people in the sample are used to gain information about the population.
c. Data from people in the population are used to gain information about the sample.
d. The population is a subset of the sample.
Q. 8A pop quiz in a class resulted in the following eight quiz scores: 0, 60, 66, 78, 82, 96, 98, 100. The five-number summary for these test scores is
a. 0, 63, 80, 97, 100.
b. 66, 78, 82, 96, 98.
c. 0, 66, 82, 98, 100.
d. 0, 25, 50, 75, 100.
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