(based on data from “Prevalence of Alcohol-Impaired Driving,” by Liu, Siegel, et al.,

Journal of the American Medical Association, Vol. 277, No. 2). Using the sample data

and a 95% confidence level, the TI-83 Plus calculator display is as shown.

a. Write a statement that interprets the confidence interval.

b. Based on the preceding result, does alcohol-impaired driving appear to be a prob-

lem for males aged 18–20? (All states now prohibit the sale of alcohol to persons

under the age of 21.)

c. When setting insurance rates for male drivers aged 18–24, what percentage of

alcohol-impaired driving would you use if you are working for the insurance com-

pany and you want to be conservative by using the likely worst case scenario?

26. Interpreting Calculator Display In 1920 only 35% of U.S. households had tele-

phones, but that rate is now much higher. A recent survey of 4276 randomly selected

households showed that 4019 of them had telephones (based on data from the U.S.

Census Bureau). Using those survey results and a 99% confidence level, the TI-83

Plus calculator display is as shown.

a. Write a statement that interprets the confidence interval.

b. Based on the preceding result, should pollsters be concerned about results from

surveys conducted by telephone?

27. Internet Shopping In a Gallup poll, 1025 randomly selected adults were surveyed and

29% of them said that they used the Internet for shopping at least a few times a year.

a. Find the point estimate of the percentage of adults who use the Internet for

shopping.

b. Find a 99% confidence interval estimate of the percentage of adults who use the

Internet for shopping.

c. If a traditional retail store wants to estimate the percentage of adult Internet shop-

pers in order to determine the maximum impact of Internet shoppers on its sales,

what percentage of Internet shoppers should be used?

28. Death Penalty Survey In a Gallup poll, 491 randomly selected adults were asked

whether they are in favor of the death penalty for a person convicted of murder, and

65% of them said that they were in favor.

a. Find the point estimate of the percentage of adults who are in favor of this death

penalty.

b. Find a 95% confidence interval estimate of the percentage of adults who are in fa-

vor of this death penalty.

c. Can we safely conclude that the majority of adults are in favor of this death

penalty? Explain.

29. Mendelian Genetics When Mendel conducted his famous genetics experiments with

peas, one sample of offspring consisted of 428 green peas and 152 yellow peas.

a. Find a 95% confidence interval estimate of the percentage of yellow peas.

b. Based on his theory of genetics, Mendel expected that 25% of the offspring peas

would be yellow. Given that the percentage of offspring yellow peas is not 25%,

do the results contradict Mendel’s theory? Why or why not?

30. Misleading Survey Responses In a survey of 1002 people, 701 said that they voted in

a recent presidential election (based on data from ICR Research Group). Voting

records show that 61% of eligible voters actually did vote.

a. Find a 99% confidence interval estimate of the proportion of people who say that

they voted.

b. Are the survey results consistent with the actual voter turnout of 61%? Why or

why not?

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