You often see margins of errors in polling results listed as ±3%. What sample size do you need to have a margin of error of at most 0.03 for a 95% confidence interval? To answer this question, set the formula for the margin of error equal to 0.03 and solve for n. In other words, solve the equation 

for n given that the multiplier = 1.96 and p? = 0.50. (Having p? = 0.50 will give you the largest possible value for n so that whatever p? you have, the sample size will give an interval with a margin of error of at most 0.03.

Transcribed Image Text:

0.03 multiplier X √p(1-P)/n