You want to estimate a population mean with a margin of erro

You want to estimate a population mean with a margin of error of ± .3 using 95% confidence interval. What is the required sample size if the standard deviation is 2.5

Solution

Compute Sample Size
n = (Z a/2 * S.D / ME ) ^2
Z/2 at 0.05% LOS is = 1.96 ( From Standard Normal Table )
Standard Deviation ( S.D) = 2.5
ME =0.3
n = ( 1.96*2.5/0.3) ^2
= (4.9/0.3 ) ^2
= 266.778 ~ 267