The α-level is the probability chosen by the researcher to be the threshold of statistical significance. It is actually the probability of committing a type I error or, essentially, of wrongly concluding that the difference between groups was the result of the intervention. The α-level is an arbitrary value but, by tradition, is usually set at 0.05, 0.01, or, less commonly, 0.001. In any event, p values less than the α-level are, by definition, “statistically significant.”