The U.S. Senate has 100 members. Information was obtained from the individuals responsible for managing correspondence in 61 senators' offices. Of these, 38 specified a minimum number of letters that must be received on an issue before a form letter in response is created.
a. Assume these observations constitute a random sample from the population, and find a 90% confidence interval for the proportion of all senators' offices with this policy.
b. In fact, information was not obtained from a random sample of senate offices. Questionnaires were sent to all 100 offices, but only 61 responded. How does this information influence your view of the answer to part (a)?