# Statistics - z-test

### Table of Contents

## About

A z-test is used when comparing a sample mean to a population mean, and the population standard deviation is known.

z-test because the distribution is in a z_scale

## Articles Related

## NHST

In a z-test, the parameters of the population are known. There is no estimation, there's not a family of sampling distributions, the distribution is just a perfectly normal.

If you were doing null hypothesis significance testing, we would expect to get, z of 0.

The actual cut-off in the z distribution with a non-directional test with alpha 0.05, is 1.96.

So if we get beyond 1.96 in a z distribution, that's going to be significant at the level of alpha .05.