What is meant by the noncritical region? The noncritical or nonrejection region is the range of test values that indicates that the difference was not due to chance and that the null hypothesis should not be rejected. The noncritical or nonrejection region is the range of test values that indicates that the difference was probably due to chance and that the null hypothesis should not be rejected. The noncritical or nonrejection region is the range of test values that indicates that the difference was probably due to chance and that the null hypothesis should be rejected