APA Dictionary of Psychology

a value used to make decisions about whether a test result is statistically meaningful. For example, to evaluate the result of a t test to determine whether a sample mean is significantly different from the hypothesized population mean, a researcher would compare the obtained test statistic to the values from a t distribution at a given probability level. If the statistic exceeds the critical value within that distribution, the null hypothesis is rejected and the result is considered significant. Also called rejection value. See also critical region.