Free Sampling Error Calculator
Calculate the maximum sampling error for a proportion at a given confidence level and sample size.
Sampling Error
0.049000
Sampling Error (%)4.9000
Standard Error of Proportion0.025000
Lower CI0.4510
Upper CI0.5490
Sampling Error vs Proportion (p)
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.
Example Calculation
A poll of 400 people finds 50% support (p = 0.5) at 95% confidence.
- 01SE = sqrt(0.5 * 0.5 / 400) = sqrt(0.000625) = 0.025
- 02Sampling error = 1.96 * 0.025 = 0.049
- 03As a percentage: +/- 4.9%
- 04CI: (0.451, 0.549) or 45.1% to 54.9%
Frequently Asked Questions
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