Question 1

What is margin of error?

Accepted Answer

The margin of error (MOE) is a statistic expressing the amount of random sampling error in a survey's results. It represents the range within which the true population value is likely to fall, given a certain confidence level.

Question 2

How is margin of error calculated?

Accepted Answer

For a simple random sample: MOE = z × √(p(1-p)/n), where z is the critical value (1.96 for 95%), p is the sample proportion (0.5 for max MOE), and n is the sample size. For finite populations, a correction factor is applied.

Question 3

What sample size do I need for a 5% margin of error?

Accepted Answer

For a 95% confidence level with maximum variability (p=0.5), you need a sample of about 384 for large populations. Use the sample size calculator to get exact numbers for your situation.

Question 4

Is this margin of error calculator free?

Accepted Answer

Yes, completely free with no signup required. All calculations run locally in your browser for full privacy.