Adoctor 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 4 points with 99 % confidence assuming s equals 12.2 based on earlier studies? suppose the doctor would be content with 90 % confidence. how does the decrease in confidence affect the sample size required?
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a 99% confidence level requires
nothing subjects. (round up to the nearest subject.)