Your firm also wants to know some things about its more than 500 investors. A survey of 43 investors shows that 14 of them are considered "passive" investors in the firm, in that they change their investment level less than twice per month (versus "active" investors who change their level more often).

a)Provide a 99% confidence interval for the percentage of investors that are passive to the nearest one-tenth of a percent.

b)What sample size would we need to provide the percentage of investors who are passive within plus or minus 10 percent at 99% confidence?

c)Suppose the firm contacted all of its investors and the 43 in the survey were the only investors that responded. What kind of sampling bias is mostly to occur in that situation (please briefly explain)?