A doctor wants to estimate the HDL cholesterol of all​ 20- to​ 29-year-old females

A doctor wants to estimate the HDL cholesterol of all​ 20- to​ 29-year-old females. How many subjects are

needed to estimate the HDL cholesterol within 4 points with 99% confidence assuming sigma = 14.8? Suppose the doctor would be content with 95 % confidence. How does the decrease in confidence affect the sample size​ required? A​ 99% confidence level requires __ subjects.