Question

In a survey, the planning value for the population proportion is p*=.25 . How large a sample should be taken to provide a 95% confidence interval with a margin of error of .06? Round your answer to next whole number.

Answer 1

Solution :

Given that,

= 0.25

1 - = 1 - 0.25= 0.75

margin of error = E = 0.06

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 / 0.06)2 * 0.25* 0.75

= 200.08

Sample size =200