In each of the following situations, evaluate whether the method of sample selection is appropriate for obtaining information about the population of interest. How would you improve the sample design?

(a) A newspaper wants to determine whether its readers believe that government expenditures should be reduced by cutting benefits for the disabled. They provide an Internet address for readers to vote yes or no. Based on 1434 Internet votes, they report that 93% of the city’s residents believe that benefits should be reduced.

(b) Acongresswoman reports that letters to her office are running 3 to 1 in opposition to the passage of stricter gun control laws. She concludes that approximately 75% of her constituents oppose stricter gun control laws.

(c) An anthropology professor wanted to compare attitudes toward premarital sex of physical science majors and social science majors. She administered a questionnaire to her large class of Anthropology 437, Comparative Human Sexuality. She found no appreciable difference between her physical science and social science majors in their attitudes, so she concluded that the two student groups were about the same in their relative acceptance of premarital sex.

(d) A questionnaire was mailed to a simple random sample of 500 household addresses in a city. Ten were returned as bad addresses, 63 were returned completed, and the rest were not returned. The researcher analyzed the 63 cases and reported that they represent a “simple random sample of city households.”

(e) A principal in a large high school is interested in student attitudes toward a proposed achievement test to determine whether a student should graduate. She lists all of the first-period classes, assigning a number to each. Then, using a random number table, she chooses a class at random and interviews every student in that class about the proposed test.