Question

If you want to be 95% confident that estimating the population mean is within a sampling error of + -200 and the standard deviation is assumed to be 1000, what is the sample size required? Round up the answer to the nearest integer.

Answer 1

Solution

standard deviation =   =1000

Margin of error = E = +/- 200

At 95% confidence level the z is ,

= 1 - 95% = 1 - 0.95 = 0.05

/ 2 = 0.05 / 2 = 0.025

Z/2 = Z0.025 = 1.96

sample size = n = [Z/2* / E] 2

n = ( 1.96* 1000 /200 )2

n =96.04

Sample size = n =96