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Mathematics

Confidence Intervals and Their Interpretation

Quick fact

A 95% confidence interval does NOT mean there is a 95% chance the true parameter lies in a given interval. The '95%' refers to the method: if you repeat the sampling and computation many times, about 95% of the resulting intervals will capture the true parameter.

Why this is interesting

You've probably seen a poll say 'the result is accurate within ±3% with 95% confidence.' But what does that actually mean? Surprisingly, it's not a 95% probability that the true value lies in that range.