Sampling Error Calculator — Formula
## How to Calculate Sampling Error for Proportions
### Formula
**Sampling Error = z * sqrt(p * (1-p) / n)**
Sampling error is the margin of error in estimating a population proportion from a sample. It depends on the confidence level (z), the proportion (p), and the sample size (n). Maximum error occurs at p = 0.5. The confidence interval is p +/- sampling error.
### Formula
**Sampling Error = z * sqrt(p * (1-p) / n)**
Sampling error is the margin of error in estimating a population proportion from a sample. It depends on the confidence level (z), the proportion (p), and the sample size (n). Maximum error occurs at p = 0.5. The confidence interval is p +/- sampling error.
Exemplo Resolvido
A poll of 400 people finds 50% support (p = 0.5) at 95% confidence.
- SE = sqrt(0.5 * 0.5 / 400) = sqrt(0.000625) = 0.025
- Sampling error = 1.96 * 0.025 = 0.049
- As a percentage: +/- 4.9%
- CI: (0.451, 0.549) or 45.1% to 54.9%