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.[28][29][30] Fisher suggested a probability of one in twenty (0.05) as a convenient cutoff level to reject the null hypothesis.[31] In a 1933 paper, Jerzy Neyman and Egon Pearson called this cutoff the significance level, which they named α {\displaystyle \alpha } . They recommended that α {\displaystyle \alpha } be set ahead of time, prior to any data collection.[31][32] 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.[31]

only 2.5 sigma