# Term:Level of Significance (a)

## NIST SP 800-22r1

Level of Significance (a) - The probability of falsely rejecting the null hypothesis, i.e., the probability of concluding that the null hypothesis is false when the hypothesis is, in fact, true. The tester usually chooses this value; typical values are 0.05, 0.01 or 0.001; occasionally, smaller values such as 0.0001 are used. The level of significance is the probability of concluding that a sequence is non-random when it is in fact random. Synonyms: Type I error, a error.