Confidence Interval Calculator
Enter how many in the sample, the mean and standard deviation, choose a confidence level, and the calculation is done live. Read Confidence Intervals to learn more.
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Standard Deviation and Mean
Use the Standard Deviation Calculator to calculate your sample's standard deviation and mean.
Caution: you should really use the standard deviation of the entire population!
But you can use the standard deviation of your sample if you have enough observations: at least n=30, the more the better.
How It Is Calculated
The Confidence Interval formula is
x̄ ± Z s√n
Where:
- x̄ is the mean
- Z is the Z-value from the table below
- s is the standard deviation
- n is the number of observations
| Z | |
| 80% | 1.282 |
| 85% | 1.440 |
| 90% | 1.645 |
| 95% | 1.960 |
| 99% | 2.576 |
| 99.5% | 2.807 |
| 99.9% | 3.291 |