with 95% confidence. How does the decrease in confidence affect the sample size required? A doctor wants to estimate the mean HDL cholesterol of all 20- to 29-year-old females. How many subjects are needed to estimate the mean HDL cholesterol within 3 points with 99% confidence assuming s = 15.7 based on earlier studies? Suppose the doctor would be content Click the icon to view a partial table of critical values. A 99% confidence level requires subjects. (Round up to the nearest subject.)