Numbers and measures
Confidence interval
- Numbers and measures
Definition
A range of values that is likely to contain the true result, given the uncertainty in your data.
Example
A mean satisfaction of 62% with a margin of 3 points gives an interval of 59% to 65%.
See how it works
Intervals calculated by a valid 95% procedure contain the true fixed parameter in about 95% of repeated samples.
Check your understanding
Common mistake: A frequentist 95% confidence interval does not mean a 95% probability that the fixed parameter is inside this particular interval.
Why report an interval as well as a point estimate?
Show explanation
The interval communicates the precision and uncertainty of the estimate.
For your role
Choose your role to see what this term means in your work.
Why it matters
It shows how certain a result is, not just the headline number.
Where it is used
Survey results, research findings and experiment reports.
How to calculate it
Mean ± (critical value × standard error)
Worked example
A mean satisfaction of 62% with a margin of 3 points gives an interval of 59% to 65%.