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.
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 |