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 14.5 based on earlier​ studies? Suppose the doctor would be content with 90 % confidence. How does the decrease in confidence affect the sample size​ required?

A​ 99% confidence level requires ____ subjects. ​(Round up to the nearest​ subject.)

Answer 1

for 99% CI:

for 99 % CI value of z=	2.576
standard deviation σ=	14.50
margin of error E =	4
required sample size n=(zσ/E)2                                         =	88.0

A​ 99% confidence level requires 88 subjects

the decrease in confidence reduces the requirement of sample size