MAXScanner calculator widget

Confidence Interval Calculator — Mean (z/t) & Proportion with Steps

Editable live calculator

Change any input — the result updates immediately

No hidden assumptions. Inputs, units and the working stay visible so you can check the calculation.

Interval for Confidence level Sample mean Standard deviation Use sample s for t mode or population σ for z mode.Sample size n Must be a whole number greater than 1.Displayed precision

Calculated result

95% CI: 65.808 to 78.192

Estimate: 72

Standard error: 3

t* (df 24): 2.064

Margin of error: 6.192

Show the working

1. SE = 15 ÷ √25 = 3.
2. Because population σ is unknown, use a two-sided t critical value with df = n−1.
3. Margin = 2.064 × 3 = 6.192.
4. Interval = 72 ± 6.192 = 65.808 to 78.192.

The t interval assumes the sample/design conditions for mean inference are reasonable. For df above 30, MAXScanner uses a standard asymptotic t-quantile expansion; differences from statistical packages should be tiny at the displayed precision.

More actions

Shared links reopen these inputs. Recent and saved calculations stay in this browser unless you clear site data.