Posted by Marnetta on .
A researcher wants to estimate the mean serum cholesterol level for college age women. In a past study the stndard devition for this measure was 42 units. If the researcher wants to be off in his estimate by no more than three units ( with 99% confidence), how large must his sample be.?

Statistics 
MathGuru,
Formula:
n = [(zvalue * sd)/E]^2
...where n = sample size, zvalue will be 2.575 using a ztable to represent the 99% confidence interval, sd = 42, E = 3, ^2 means squared, and * means to multiply.
Plug the values into the formula and finish the calculation. Round your answer to the next highest whole number.