how many respondents needed
How Many Respondents Do I Need? Sample Size Guide
This high-intent guide translates statistical parameters into practical respondent targets.
How to calculate using Sample Size Calculator
- Select confidence level and desired margin of error.
- Set estimated proportion p; use 50% if unknown for conservative sizing.
- Apply finite population correction if population size is known.
Sample Size Calculator formula
- Initial size n0 = z^2 x p(1-p) / e^2.
- Finite correction n = n0 / (1 + (n0-1)/N).
- Final sample size is rounded up to next whole number.
Worked example
- 95% confidence, 5% margin, p=50% gives n around 385.
- If population is finite, corrected sample can be lower.
- Always round up, not down.
Accuracy and interpretation notes
- Do not confuse sample size with response rate; account for nonresponse separately.
- Set realistic margin of error for project budget and timeline.
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