a) A manufacturer of golf equipment wishes to estimate the number of left-handed golfers in the U.S. How large of a sample is needed in order to be 99% confident that the sample proportion will not differ from the population proportion by more than 3%?
b) In order to set rates, an insurance company is trying to estimate the number of sick days that full time workers at an auto repair shop take per year. A previous study indicated that the population standard deviation was 2.1 days. How large a sample must be selected if the company wants to be 92% confident that the population mean differs from the sample mean by no more than 1/2 day?