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# Z-Test calculator

Run one or two sample and one or two proportion z tests and get the statistic, p value, critical value, and a plain decision.

Fill in the fields for your test kind to see the statistic.

A z-test assumes the spread is known, not estimated from your sample. If you only have the sample SD, a t-test is the honest choice, and this tool will not pretend otherwise. A significant result at your alpha is a statement about long-run frequencies, not proof that this particular difference is real.
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## More unit & math tools

- [Average and median](/converters/statistics)
- [Unit converter](/converters/units)
[All unit & math tools](/converters)

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