Proportion Margin of Error Estimate
Proportion Margin of Error Estimate with explicit assumptions and reproducible inputs.
Formula
- Use the units shown beside each field.
- Results update automatically whenever you change an input.
- Displayed values use up to four decimal places, or scientific notation for very small or large numbers. Calculations use standard floating-point arithmetic; exact integer and fraction tools identify their own precision rules.
- Normal-approximation planning estimate for independent simple random sampling, without a finite-population correction. Not an exact confidence interval for sparse observed counts.
Example Calculation
- Planning proportion p: 0.5
- Planned sample size: 400
- Confidence level: 95 %
At p=0.5, n=400 and 95% confidence, the planned margin is approximately 0.049, or 4.9 percentage points.
Method references
Frequently asked questions
How do I use this calculator?
Enter planning proportion p, planned sample size, confidence level. The result updates automatically. Use Reset to restore the example values.
What method does it use?
Approximate margin=z√[p(1−p)/n]. Normal-approximation planning estimate for independent simple random sampling, without a finite-population correction. Not an exact confidence interval for sparse observed counts.
Why might a rounded result differ?
The calculation keeps full numeric precision internally, then rounds the displayed result. Rounding intermediate steps by hand can produce a slightly different answer.
Are my inputs saved online?
No. This calculator processes your inputs in your browser. A recently used list stores only calculator names on this device, not your entered values.
Check the assumptions and units before using this result. Read about calculation methods.