Proportion Margin of Error
Estimate a normal-approximation margin from sample size and proportion.
Your numbers
Margin of error
This Wald approximation is unreliable for small samples or proportions near zero or one; use Wilson or exact intervals instead.
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Formula
E = z√(p(1−p)/n)
Estimate a normal-approximation margin from sample size and proportion.
Worked example
- Proportion (%)
- 50
- Sample size
- 400
- Confidence level (%)
- 95
- Margin of error
- 4.89990996135 percentage points
Scope and limitations
This Wald approximation is unreliable for small samples or proportions near zero or one; use Wilson or exact intervals instead.
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Formula version: a64ddcc9dcae · Example checked: