Significance level: The predetermined threshold used to determine whether to reject or fail to reject the null hypothesis. Commonly used levels are 0.05 (5%) and 0.01 (1%).
Test statistic: A value calculated from sample data used to make decisions about rejecting or failing to reject the null hypothesis.
Critical region: The range of values for which, if the test statistic falls within it, we would reject the null hypothesis in favor of the alternative hypothesis.