Do I need to install anything?

No. It runs in any modern browser, free, with no account required.

For Engineers · Confidence Intervals

Confidence Intervals for a survey sample

Built for engineers using it for real design work. Go from concept to a running model in the browser, then scale to the cloud when needed. Simulate a survey sample live below — adjust the inputs and watch it respond, right in your browser.

Confidence IntervalsLive

what 95% really means

Controls

Presets

Sample size n

A confidence interval is often misread. It does not mean the true value has a 95% chance of being in one interval — it means that if you repeated the experiment many times, about 95% of the intervals would contain the true mean. The red intervals here are the unlucky ones that miss it.

▶ Run in Python

Data Inspector

Confidence level95%

Observed coverage0%

Intervals shown50

Governing equation

\overset{x}{ˉ} \pm z \frac{σ}{n} = 50 \pm 1.96 \cdot \frac{10}{30}

Reading this result: About 0% of these 50 intervals captured the true mean — close to the 95% you asked for. Raising n from 30 tightens each interval (SE = σ/√n) but does not change that hit rate: the confidence level, not the sample size, sets how often you are right.

Runs locally in your browser — free forever. Scale to the cloud when reality gets heavy.

or unlock everything with Pro →

Also for:Students Researchers Educators Hobbyists & Makers K-12 Students First Responders General version →

More with Confidence Intervals

Confidence Intervals for an A/B test Confidence Intervals for a poll margin Confidence Intervals for a quality-control chart Confidence Intervals for a clinical trial Confidence Intervals for a customer churn Confidence Intervals for a click-through rate Confidence Intervals for an exam-score curve Confidence Intervals for a defect rate

Frequently asked questions

Is this good for engineers?: Yes — this version of "Confidence Intervals for a survey sample" is framed for engineers using it for real design work. Go from concept to a running model in the browser, then scale to the cloud when needed.
Do I need to install anything?: No. It runs in any modern browser, free, with no account required.