Sample Size Calculator

Find the sample size for a target margin of error.

Required sample size 385

Formula: n = z² · p(1−p) ÷ MOE²

Step-by-step with your numbers:

1. Values used:

2. Margin of error = 0.05

3. Expected proportion = 0.5

4. Confidence level = 1.96

6. Required sample size = 385

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The math behind it

n = z² × p(1−p) ÷ margin². Use p = 0.5 for the most conservative (largest) sample.

95%, ±5%, p 0.5 → 385.

Why p = 0.5?

It maximizes p(1−p), giving the safest (largest) sample size.