sample size calculator
Sample Size Calculator for Surveys and Research
Underpowered surveys produce unreliable conclusions. This article helps you estimate sample size before data collection.
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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