Question

What sample size is needed to give a margin of error of 5% with a 95% confidence interval?
Sample size =

Answer 1

Solution :

Given that,

= 0.5

1 - = 1 - 0.5 = 0.5

margin of error = E = 5% = 0.05

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 * * (1 - )

   = (1.96 /0.05)2 * 0.5 * 0.5

= 384

sample size = n = 384