A researcher wants to estimate the mean serum cholestreol le

A researcher wants to estimate the mean serum cholestreol level for college age women. In a past study the standard deviation 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?

Solution

Given a=0.01, Z(0.005) = 2.58 (from standard normal table)

So n=(Z*s/E)^2

=(2.58*42/3)^2

=1304.654

Take n=1305