In a study of 500 executives, 315 stated that their company informally monitored social networking sites to stay on top of information related to their company. (Data extracted from "Checking Out the Buzz," USA Today, June 26, 2009, p. 1B.)
a. Construct a 95% confidence interval for the proportion of companies that informally monitored social networking sites to stay on top of information related to their company.
b. Interpret the interval constructed in (a).
c. If you wanted to conduct a follow-up study to estimate the population proportion of companies that informally monitored social networking sites to stay on top of information related to their company to within with 95% confidence, how many executives would you survey?