We need to estimate the average of a population and from mea

We need to estimate the average of a population and from mea- surements on similar populations we estimate that s2 = 8. Find the sample size n such that we are 90 percent confident that the estimate of x is within ±1 unit of the true mean .

Solution

Compute Sample Size
n = (Z a/2 * S.D / ME ) ^2
Z/2 at 0.1% LOS is = 1.64 ( From Standard Normal Table )
Standard Deviation ( S.D) = Sqrt(8) = 2.83
ME =1
n = ( 1.64*2.83/1) ^2
= (4.641/1 ) ^2
= 21.541 ~ 22