Sample Size accuracy and testing

Formula source

• The calculator uses **Cochran's Formula** for infinite populations, adjusted for finite populations if a size is provided. **n = (Z² × p(1-p)) / e²** * **Z**: Z-score for confidence level (e.g., 1.96 for 95%) * **p**: Population proportion (assumed 50% for maximum sample size) * **e**: Margin of error (decimal)

Test cases

Known limitations

• This page documents the checked-in calculator logic and does not certify results for every real-world edge case.
• Use the result as a planning estimate unless the calculator page states a stricter purpose.

Assumptions

• Margin of error should be a positive percentage and distribution should be between 0% and 100%.
• The calculator uses Cochran's formula with a finite population correction when a population size is supplied.
• Using a 50% distribution gives the most conservative sample-size estimate when the true proportion is unknown.

Unit handling

• Confidence Level accepts one of the configured options.
• Margin of Error accepts values in %.
• Population (Optional) accepts numeric values.
• Distribution accepts values in %.

Rounding rules

• Number displays use up to 2 decimal places in the calculator UI.

Version history

Change log