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.
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 a large enough sample: at least n=30, the more the better.
How It Is Calculated
The Confidence Interval formula is
X ± Z | s |
√(n) |
Where:
- X is the mean
- Z is the Z-value from the table below
- s is the standard deviation
- n is the number of samples
Z | |
80% | 1.282 |
85% | 1.440 |
90% | 1.645 |
95% | 1.960 |
99% | 2.576 |
99.5% | 2.807 |
99.9% | 3.291 |