The significance level sets how demanding the decision threshold will be. Because the critical value is determined partly by this chosen level, changing it changes the boundary of the critical region. A calculated statistic may therefore lead to rejection at one significance level but not another. This makes the decision rule explicitly dependent on the selected level of evidence against the null hypothesis.
The distribution supplies the reference pattern for sampling variability, so it determines which threshold is appropriate for a particular test statistic. A z-based comparison uses the z distribution, whereas other analyses may require t, chi-square, or F distributions. Matching the statistic to its relevant distribution keeps the critical region aligned with the null model being evaluated.
Entry depends on the statistic’s position relative to the critical value selected for the test, not simply on whether an observed effect, difference, or association exists. When the statistic falls in the critical region, the result meets the prespecified decision rule for rejecting the null hypothesis. The comparison therefore connects numerical evidence with a reproducible statistical conclusion.
A noticeable effect, difference, or association must still be interpreted against sampling variability under the null model. The comparison provides a rule for deciding whether the calculated statistic is sufficiently separated from the null expectation to support rejection. It helps distinguish an observed pattern from evidence judged unlikely under the chosen testing framework and significance level.
First, identify the null hypothesis and the test statistic being calculated. Next, choose the significance level and the probability distribution relevant to that statistic, then obtain the corresponding critical value. Finally, compare the calculated statistic with the threshold and determine whether it lies in the critical region. This sequence produces a clear and reproducible decision rule.
Selection follows the probability distribution relevant to the calculated test statistic and the analysis being conducted. The method can therefore use z, t, chi-square, or F critical values rather than one universal threshold. Correct distribution matching is essential because the threshold must represent the sampling variability described by the chosen null-model framework.