Sampling Distribution of Proportion

Assume a population of size NN with a known proportion of successes pp.

By drawing all possible samples of size nn and calculating their sample proportions p‾i\overline{p}_i, the sampling distribution of the success proportion can be computed.

Mean

Average of all sample proportions p‾i\overline{p}_i, denoted as p‾\overline{p}, is pp.

Standard Error

σp=p(1−p)n\sigma_p = \sqrt{\frac{p(1-p)}{n}}

Approx. to Normal Distribution

If the below conditions are met:

  • The sample size is large enough.
  • The population proportion is known.

Then:

p‾∼N(p,p(1−q)n)\overline{p} \sim N \left(p,\frac{p(1-q)}{n} \right)
Written by September 29, 2026 1 min read
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