Confidence Level Calculator
Sample Size (n)
Proportion (%)
Confidence Level
A confidence interval gives a range likely containing the true population value. 95% CI: if the same study were repeated 100 times, ~95 intervals would contain the true value.
- 1Margin of error = z × √(p(1−p)/n)
- 2z = 1.96 for 95% CI; 2.576 for 99%
- 3Larger sample n → smaller MOE → more precise interval
- 4CI = point estimate ± margin of error
n=1,000, 50% proportion, 95% CI=MOE = ±3.1%; CI = [46.9%, 53.1%]
| Level | Z-score |
|---|---|
| 90% | 1.645 |
| 95% | 1.960 |
| 99% | 2.576 |
| 99.9% | 3.291 |
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