Calculate the standard error of a mean and how it shrinks with sample size.
Because standard error scales with the square root of n, halving it requires quadrupling the sample. That square-root relationship is the fundamental economics of sampling. Doubling a survey sample improves precision by only about 30 per cent, which is why very large samples deliver diminishing returns.
Standard Error
SE = s ÷ √n; required n = (s ÷ target SE)²
SE = s ÷ √n; required n = (s ÷ target SE)² Because standard error scales with the square root of n, halving it requires quadrupling the sample. That square-root relationship is the fundamental economics of sampling.
Doubling a survey sample improves precision by only about 30 per cent, which is why very large samples deliver diminishing returns.
This calculator takes 3 inputs: Sample standard deviation, Sample size, Target standard error. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.