Find the sample size needed to provide a margin of error of

. Find the sample size needed to provide a margin of error of 7 or less with a .99 probability when the population standard deviation is 12.

Solution

Compute Sample Size
n = (Z a/2 * S.D / ME ) ^2
Z?/2 at 0.01% LOS is = 2.58 ( From Standard Normal Table )
Standard Deviation ( S.D) = 12
ME =7
n = ( 2.58*12/7) ^2
   = (31/7 ) ^2
   = 19.6 ~ 20