Determining sample size

Question

Find The minimum sample size needed to estimate the proportion of voters favoring a candidate if we want our estimate to be within 3.2% as the margin of error and a confidence level of 90%. A sample proportion of 85% was given.

Answer 1

The steps for finding the minimum sample size required to estimate a population proportion

X = Z_α/2² *p*(1-p) / MOE², and Z_α/2 is the critical value of the normal distribution at α/2 (e.g. for a confidence level of 95%, α is 0.05 and the critical value is 1.96), MOE is the margin of error, p is the sample proportion, and N is the population size.