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Confidence interval (CI)


Quantifies the uncertainty in measurement. It is usually reported as 95% CI, which is the range of values within which we can be 95% sure that the true value for the whole population lies. For example, for an NNT of 10 with a 95% CI of 5 and 15, we would have 95% confidence that the true NNT value was between 5 and 15.

Confidence intervals are dealt with in a longer downloadable PDF.

A caveat is that the confidence interval relates to the population sampled. If we have a small sample of part of a population, or a very small sample of the whole population, then the confidence interval that is generated is not necessarily that for the whole population.