Confidence interval

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%.

A 95% confidence level is not defined as 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][3] In other words, this indicates that if the same sampling procedure were repeated 100 times from the same population, approximately 95 of the resulting intervals would be expected to contain the true population mean (see the figure). In this framework, the parameter to be estimated is not a random variable (since it is fixed, it is immanent), but rather the calculated interval, which varies with each experiment.[2]

  1. ^ Hazra, Avijit (2017). "Using the confidence interval confidently". Journal of Thoracic Disease. 9 (10): 4124–4129. doi:10.21037/jtd.2017.09.14. PMC 5723800. PMID 29268424.
  2. ^ a b Cite error: The named reference Dekking was invoked but never defined (see the help page).
  3. ^ "Confidence Intervals". Yale Department of Statistics. Retrieved 2025-04-05.
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