A political candidate has asked you to conduct a poll to determine what percentage of people support her.

Question

A political candidate has asked you to conduct a poll to determine what percentage of people support her.

If the candidate only wants a 1% margin of error at a 90% confidence level, what size of sample is needed?

Give your answer in whole people.

Answer 1

p=0.5 (default since no value is given)

q=1-0.5=0.5

margin of error=5%=0.05

z_c=1.65 at 90% confidence.

margin of error: e= sqrt(p(1-p)/n)*z_c

or, 0.05=sqrt(0.5*0.5/n)*1.65

or, n= (0.5*1.65/0.05)^2=272.25

The required sample size=273