StatReasonConfidence Intervals & Estimation
A single number from a sample is only ever an estimate. These tools express how precise that estimate is with an interval, always shown alongside its estimate, standard error, confidence level, and method, since a bare interval without knowing how it was built is not enough to interpret responsibly.
Every engine here states which method it uses (a t interval, a Wilson score interval, a Fisher z transform) explicitly rather than silently picking one, because different methods make different assumptions and give different intervals on the same data.
Engines in this category
- Mean Confidence Interval Calculator
Estimate a population mean from a sample, with a stated margin of uncertainty.
- Proportion Confidence Interval Calculator
Estimate a binomial proportion with a defensible interval, not a bare percentage.
- Margin of Error Calculator
Find the sampling precision for a proportion given a sample size.
- Difference of Means Confidence Interval Calculator
Estimate the gap between two independent group means with a Welch interval.
- Paired Difference Confidence Interval Calculator
Estimate the mean change between matched pairs with a t interval.
- Correlation Confidence Interval Calculator
Give a Fisher z interval around a Pearson correlation, not just a point estimate.
- Confidence Interval Calculator
Route to the right confidence interval method for your design, not one generic answer.
- Difference in Proportions Confidence Interval
Estimate the absolute risk difference between two independent proportions.
- Odds Ratio Confidence Interval Calculator
Estimate association from a 2 by 2 table with a log-odds Wald interval.
- Risk Ratio Confidence Interval Calculator
Estimate relative risk from cohort-style exposure and event counts.