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Data & Analytics · Intermediate

Student's t-Test

A test comparing means (one sample against a value, or two independent groups) when the population standard deviation is unknown, using the t-distribution.

Definition

t-tests assume approximately normal data or large samples and independent observations. Welch's t-test does not assume equal variances. With more than two groups, use ANOVA.

Example

Comparing average basket size between two store layouts.

Exam tip

Two group means = t-test; three or more = ANOVA; σ unknown or small n = t rather than z.

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