Confidence interval

This article needs attention from an expert in statistics. The specific problem is: This article may be too technical for most readers to understand. WikiProject Statistics may be able to help recruit an expert. (April 2025)

In statistics, a confidence interval (CI) is a range of values used to estimate an unknown statistical parameter, such as a population mean.^[1] Rather than reporting a single point estimate (e.g. "the average screen time is 3 hours per day"), a confidence interval provides a range, such as 2 to 4 hours, along with a specified confidence level, typically 95%. This indicates that if the same sampling procedure were repeated 100 times, approximately 95 of the resulting intervals would be expected to contain the true population mean, and we call such intervals as 95% confident interval for the mean.

Increasing the confidence level increases the sizes of confidence intervals. In an extreme case, 100 % confidence level results a very large, probably infinite, length of a confidence interval, that is of course not useful.

A 95% confidence level does not imply a 95% probability that the true parameter lies within a particular calculated interval. The confidence level instead reflects the long-run reliability of the method used to generate the interval.^[2]