How this calculation works
Express the loss of precision from unequal positive survey weights as an equivalent sample size.
THE FORMULA
n_eff=(Σwᵢ)²/Σwᵢ²A worked example
Weights 1, 2, 3 and 4 have an effective sample size of 3⅓.
Good to know
This weight-only measure does not account for clustering or stratification.
Reference: OpenStax Introductory Statistics (opens in a new tab) ↗
Read the result
Express the loss of precision from unequal positive survey weights as an equivalent sample size.
The primary result is labeled “Effective sample size”. Keep the input definitions in view when comparing this result with another method.
Try a related calculation
This weight-only measure does not account for clustering or stratification.
For a related exercise, try the statistics calculator.
A few questions, answered
How can I check the default inputs by hand?
Weights 1, 2, 3 and 4 have an effective sample size of 3⅓.
Which rule does this calculator apply?
n_eff=(Σwᵢ)²/Σwᵢ²