Time magazine, in an article in the late 1950s, stated that "the average Yaleman, class of 1924, makes $25,111 a year," which, in today's dollars, would be over $150,000. Time's estimate was based on replies to a sample survey questionnaire mailed to those members of the Yale class of 1924 whose addresses were on file with the Yale administration in the late 1950s.

a. What is the survey's population of interest?

b. Were the techniques used in selecting the sample likely to produce a sample that was representative of the population of interest?

c. What are the possible sources of bias in the procedures used to obtain the sample?

d. Based on the sources of bias, do you believe that Time's estimate of the salary of a 1924 Yale graduate in the late 1950s is too high, too low, or nearly the correct value?