A doctor wants to estimate HDL cholesterol level of all 20 t

A doctor wants to estimate HDL cholesterol level of all 20 to 29 year old females. How many subjects are needed to estimate within 3 points wi 99% confidence assuming variance=10.6? Suppose the doctor would be content with 90% confidence. How does the decease in confidence affect the sample size required.

Solution

A doctor wants to estimate HDL cholesterol level of all 20 to 29 year old females. How many subjects are needed to estimate within 3 points wi 99% confidence assuming variance=10.6? Suppose the doctor would be content with 90% confidence. How does the decrease in confidence affect the sample size required.

Sample size

For 99%, z=2.576

d=3

variance =10.6

Sample size = (z²*s²)/d²

= (2.576²*10.6)/3²

=7.8

The sample size required= 8

The decrease in confidence will decrease the sample size required.

For 90%, z=1.645

n= (1.645²*10.6)/3²

=3.18

The sample size required= 4