Statistics & Probability
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Z-Test Statistic

Tests whether a sample mean differs from a hypothesized value.

Formula

z=xˉμ0σ/nz = \frac{\bar{x} - \mu_0}{\sigma/\sqrt{n}}

Variables

\bar{x}Sample mean
\mu_0Hypothesized mean

Example

Compare to critical z

Did You Know?

The z-test assumes a known population standard deviation, a luxury so rare that the t-test usually replaces it.