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 9% margin of error at a 90% confidence level, what size of sample is needed?

Give your answer in whole people.

Answer 1

Using default of proportion

P=0.5(since no value is given)

q=1-0.5=0.5

Margin of error =9%=0.09

Z_c=1.65 at 90% confidence interval

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

or, 0.09=sqrt(0.5*0.5/n)*1.65

or, n= (0.5*1.645/0.09)^2=84.0277

The required sample is 84