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 22 points with 99 % confidence assuming s equals 13.7 based on earlier​ studies? Suppose the doctor would be content with 95 % confidence. How does the decrease in confidence affect the sample size​ required?

a) A​ 99% confidence level requires _____subjects.

b) A 95 % confidence level requires _____ subjects. ​

Answer 1

ANSWER:

Is it within 2 points or 22 points? I have taken 22, take 2 in denominator if it is 2.

When confidence level is 99%

n = [z * s/E]^2

n = [2.5758*13.7/22]^2

n = 1.2665

When confidence level is 95%

n = [z * s/E]^2

n = [1.960*13.7/22]^2

n = 1.490

As confidence level decreases, number of samples required also decrease.

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