The average years of employee experience at any company is normally distributed, with a standard deviation of 12 years. If a sample of 50 employees indicates a mean age is 38 year.
a) Calculate a 90% confidence interval for the population mean.
b) How many employees should we sample if we want to change the ME to 2.5 with 90% confidence?
c) Calculate a 99% confidence interval for the population mean.
d) How many employees should we sample if we want to change the ME to 3.9 with 99% confidence?