Confidence interval
A range printed after a test score, like 84 (79 to 91). It is the test's honest way of saying the single number is an estimate, and the true score most likely sits inside that range.
Applies across the UK
When a report gives a score as '84 (95% confidence interval 79 to 91)', it is telling you two things: the best estimate, and how sure the test can be about it. The Office for National Statistics describes a confidence interval as specifying a range of values likely to contain the unknown population value, which for a test means the score the test is trying to estimate.
For a test score, it means this: no test can measure a child to a single exact point. The 84 is the middle of the range, and your child's true score most likely sits somewhere between 79 and 91.
This range matters most when a score sits near a cut-off Cut-off A line drawn through a range of scores. On one side a service may offer an assessment or support, on the other side it may not. Read the full definition of Cut-off . If a service treats 84 as an exact fact and the cut-off is 85, the confidence interval is your honest, technical way of pushing back: the test itself does not claim that precision. And a wider interval means more uncertainty in the measurement, never a worse child.
Related words
Where this comes from
- Uncertainty and how we measure it for our surveys , Office for National Statistics. Checked 2026-08-14.
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