Question

A political candidate has asked you to conduct a poll to determine what percentage of people support him. If the candidate only wants a 0.5% margin of error at a 95% confidence level, what size of sample is needed?

Answer 1

Solution :

Given that,

= 1 - = 0.5

margin of error = E = 0.005

At 95% confidence level

= 1 - 95%

=1 - 0.95 =0.05

/2 = 0.025

Z/2 = 1.96

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

= (1.96 / 0.005)² * 0.5 * 0.5

sample size = n = 38416