Confidence intervals for means and proportions.
Computed with standard statistical methods in your browser.
For a mean, the margin of error is z·(SD ÷ √n); for a proportion it’s z·√(p(1−p)/n). The interval is your estimate plus and minus that margin.
Run the rest of your analysis with our other free stats tools.
A range that likely contains the true population value at a chosen confidence level.
z × standard error, where the standard error depends on SD (means) or p (proportions).
This tool uses z, which is fine for large samples; very small samples technically use t.
About 95% of intervals built this way would capture the true value over repeated sampling.
Use mean for numeric data and proportion for percentages or yes/no rates.