Editing Confidence interval (section)

{{Short description|Range to estimate an unknown parameter}}
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[[File:Normal distribution 50% CI illustration.svg|thumb|upright=1.3|Each row of points is a sample from the same normal distribution. The colored lines are 50% confidence intervals for the population mean ''μ''. At the center of each interval is the sample mean <math display="inline">\bar{x}</math>, marked with a diamond. The blue intervals contain ''μ'', and the red ones do not. 50 % of all intervals (blues) have the population mean.]]

In [[statistics]], a '''confidence interval''' ('''CI''') is a range of values used to estimate an unknown [[statistical parameter]], such as a population [[mean]].<ref name="using_confidently">{{cite journal | doi=10.21037/jtd.2017.09.14 | doi-access=free | title=Using the confidence interval confidently | date=2017 | last1=Hazra | first1=Avijit | journal=Journal of Thoracic Disease | volume=9 | issue=10 | pages=4124–4129 | pmid=29268424 | pmc=5723800 }}</ref> 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.

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.<ref>{{Cite web |title=Confidence Intervals |url=http://www.stat.yale.edu/Courses/1997-98/101/confint.htm |website=Yale Department of Statistics |access-date=2025-04-05}}</ref>