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Confidence interval calculator
Intervals for a mean use the t distribution; intervals for a proportion use the Wilson score method, which is more accurate than the textbook normal approximation, particularly with small samples or proportions near 0 or 1.
An interval shows both whether an effect is distinguishable from zero and how precisely you have measured it. Reviewers increasingly ask for intervals in place of, not alongside, bare significance.
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This calculator was checked by Sidra Khan, Lead Biostatistician
In short
What is a confidence interval?
A confidence interval is a range of plausible values for a population parameter, calculated from sample data. A 95% interval means that if the study were repeated many times, 95% of the intervals produced would contain the true value. It does not mean there is a 95% probability that the true value lies within this particular interval.
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