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Calculate the minimum sample size needed for surveys and experiments based on confidence level and margin of error.
| Margin of Error | 90% Confidence | 95% Confidence | 99% Confidence |
|---|---|---|---|
| ±1% | 6,765 | 9,604 | 16,587 |
| ±3% | 752 | 1,067 | 1,843 |
| ±5% | 271 | 384 | 663 |
| ±10% | 68 | 96 | 166 |
50% gives the maximum sample size because p(1-p) is maximized at p=0.5. If you're unsure, use 50% to ensure your sample is large enough.
For populations over 20,000, the finite population correction has minimal effect. It becomes significant for smaller populations, allowing smaller samples.