Posted by Megan on .
A doctor wants to estimate the HDL cholesterol of all 2029 year old females. How many subjects are needed to estimate the HDL cholesterol within 2 points with 99%confidence assuming s=17.8 based on earlier studies? Suppose the doctor would be content with 90% confidence. How does the decrease in cofidence affect the sample size required?
A: A 99% confidence level requires ___ subjects
B: A 90% confidence level requires ___ subjects

7 STATS MATHGURU PLEASE HELP 
MathGuru,
2.58 = 99% confidence interval
1.645 = 90% confidence interval
Use a formula to find sample size.
Here is one:
n = [(zvalue * sd)/E]^2
...where n = sample size, zvalue = values above for the intervals needed, sd = 17.8, E = .02, ^2 means squared, and * means to multiply.
Plug the values into the formula and finish the calculations. Round your answers to the next highest whole number.
I'll let you take it from here. 
7 STATS MATHGURU PLEASE HELP 
hi,
A doctor wants to estimate the mean HDL cholesterol of all 20 to 29yearold females. How many subjects are needed to estimate the mean HDL cholesterol within 44 points with 99 %99% confidence assuming s equals 11.2s=11.2 based on earlier studies? Suppose the doctor would be content with 90 %90% confidence. How does the decrease in confidence affect the sample size required?