📊 Confidence Interval Calculator
Calculate confidence intervals
How Confidence Intervals Are Calculated
- 1Enter the sample mean (or proportion), standard deviation, and sample size.
- 2Select the confidence level (90%, 95%, or 99%).
- 3The calculator applies the formula: CI = x̄ ± z*(σ/√n) and displays the interval.
About Confidence Interval Calculator
Calculate confidence intervals for means and proportions. Supports 90%, 95%, and 99% confidence levels with step-by-step formulas.
Frequently Asked Questions
What does 95% confidence mean?
If you repeated the sampling 100 times, about 95 of those intervals would contain the true population parameter.
How do I reduce the interval width?
Increase sample size, lower the confidence level, or reduce variability in your data.