Question

find the sample size required to estimate the true population of Professors with PhDs who like to be called doctor with error +/-.05 and 95% confidence. Pi=0.5

Answer 1

Solution:

Given that,

= 0.5

1 - = 1 - 0.5 = 0.5

margin of error = E = 0.05

At 95% confidence level the z is ,

= 1 - 95% = 1 - 0.95 = 0.05

/ 2 = 0.05 / 2 = 0.025

Z_/2 = Z_0.025 = 1.960

Sample size = n = ((Z _{/ 2}) / E)² * * (1 - )

= (1.960 / 0.05)² * 0.5 * 0.5

= 384.15

= 384

n = sample size = 384