Question

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 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.)

Answer 1

confidence coefficient for 90% is 1.64

Explanation:

confidence coefficient for 99% is 2.58

2.58 * 19.4/sqrt(n) = 0.04

2.598*19.4/0.04 = sqrt(n)

( 2.598*19.4/0.04)^2 = n

1587676

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confidence coefficient for 90% is 1.64

is this right?