<P> The term significance does not imply importance here, and the term statistical significance is not the same as research, theoretical, or practical significance . For example, the term clinical significance refers to the practical importance of a treatment effect . </P> <P> In 1925, Ronald Fisher advanced the idea of statistical hypothesis testing, which he called "tests of significance", in his publication Statistical Methods for Research Workers . Fisher suggested a probability of one in twenty (0.05) as a convenient cutoff level to reject the null hypothesis . In a 1933 paper, Jerzy Neyman and Egon Pearson called this cutoff the significance level, which they named α . They recommended that α be set ahead of time, prior to any data collection . </P> <P> Despite his initial suggestion of 0.05 as a significance level, Fisher did not intend this cutoff value to be fixed . In his 1956 publication Statistical methods and scientific inference, he recommended that significance levels be set according to specific circumstances . </P> <P> The significance level α is the threshold for p below which the experimenter assumes the null hypothesis is false, and something else is going on . This means α is also the probability of mistakenly rejecting the null hypothesis, if the null hypothesis is true . </P>

Hypothesis test at the 5 level of significance