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

Question

If the candidate only wants a 9% margin of error at a 90% confidence level, what size of sample is needed?

Answer 1

z-critical = 1.645

margin of error = 0.09

n = 0.25 (1.645/0.09)^2 = 83.5 ~ 84