Question

At 95% confidence, how large a sample should be taken to obtain a margin of error of .015 for the estimation of a population proportion? Assume that past data are not available for developing a planning value for P* . Round up to the next whole number.

Answer 1

Solution :

Given that,

= 0.5 ( assume 0.5)

1 - = 1 - 0.5= 0.5

margin of error = E =0.015

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 ( Using z table )

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

= (1.96 / 0.015)2 * 0.5 * 0.5

= 4268.44

Sample size =4269