significance level

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun Used other than as an idiom: see significance,‎ level.
• noun statistics A measure of how likely it is to draw a false conclusion in a statistical test, when the results are really just random variations.
• noun statistics The probability, usually expressed as a percentage, of making a decision to reject the null hypothesis when the null hypothesis is actually true; the probability of making a type 1 error).