Editing Z-test (section)

{{Short description|Statistical test}}
{{DISPLAYTITLE:''Z''-test}}
{{redirect-multi|1|Z test|the "Z-test" procedure in the [[graphics pipeline]]|Z-buffering}}
{{nofootnotes|date=May 2020}}
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A '''''Z''-test''' is any [[statistical hypothesis testing|statistical test]] for which the [[probability distribution|distribution]] of the [[test statistic]] under the [[null hypothesis]] can be approximated by a [[normal distribution]]. ''Z''-test tests the mean of a distribution. For each [[statistical significance|significance level]] in the [[Confidence intervals|confidence interval]], the ''Z''-test has a single critical value (for example, 1.96 for 5% two-tailed), which makes it more convenient than the [[Student's t-test|Student's ''t''-test]] whose critical values are defined by the sample size (through the corresponding [[degrees of freedom (statistics)|degrees of freedom]]). Both the ''Z''-test and Student's ''t''-test have similarities in that they both help determine the significance of a set of data. However, the ''Z''-test is rarely used in practice because the population deviation is difficult to determine.{{cn|date=May 2025}}