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Data & Analytics · Intermediate

Central Limit Theorem (CLT)

The theorem that the distribution of sample means approaches a normal distribution as sample size grows, regardless of the population's shape.

Definition

A sample size of about 30 or more is a common rule of thumb. The CLT justifies confidence intervals and tests on means even for non-normal data, with standard error σ/√n.

Exam tip

The CLT applies to sample means (and sums), not to individual observations.

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