Families USA, a monthly magazine that discusses issues related to health and health costs, surveyed 20 of its subscribers. It found that the annual health insurance premiums for a family with coverage through their employers averaged $10,979. The standard deviation of the sample was 1,000.
A. Based on the sample information, develop a 90% confidence interval for the population mean yearly premium.
B. How large a sample is needed to find the population mean within $250 at 99% confidence?