In hypothesis testing what is the function of a critical val

In hypothesis testing, what is the function of a critical value?

Solution

The critical value is the value that the test statistic needs to surpass (towards the extremes) so that the null hypothesis will be rejected.

For example, in a z test, of the critical value is zcrit = 1.65, then the test statistic z must surpass 1.65 for the null hypothesis to be rejected.