Enter the sample proportion p and sample size n to compute SE = sqrt[p(1-p)/n], the sampling variability of a proportion estimate, for proportion confidence intervals and tests.
输入样本比例 p 与样本量 n，求比例标准误。
| Item | Formula / Note | Source / Standard |
|---|---|---|
| Standard error of a proportion | SE = sqrt( phat · (1 - phat) / n ) | Cochran WG, Sampling Techniques (3rd ed., 1977) |
| Wald confidence interval | phat ± z · SE | Cochran WG, Sampling Techniques (3rd ed., 1977) |
| Normal approximation condition | Approximation is adequate when n·phat >= 10 and n·(1 - phat) >= 10 | NIST/SEMATECH e-Handbook of Statistical Methods §1.3.6.6 |
| Worst case | SE is maximized at phat = 0.5, giving SE = 0.5 / sqrt(n) | Cochran WG, Sampling Techniques (3rd ed., 1977) |