The critical value (CV) is used in significance testing to establish the critical and noncritical regions of a distribution. If the test value or statistic falls within the range of the critical region (the region of rejection), then there is a significant difference or association; thus, the null hypothesis should be rejected. Conversely, if the test value or statistic falls within the range of the noncritical region (also known as the nonrejection region), then the difference or association is possibly due to chance; thus, the null hypothesis should be accepted.

When using a one-tailed test (either left-tailed or right-tailed), the CV will be on either the left or the right side of the mean. Whether the CV is on the left or right side of ...