statistical error type I error Brian S. Alper, Harold Lehmann, Kenneth Wilkins, Joanne Dehnbostel, Muhammad Afzal false positive error Incorrectly rejecting the null hypothesis' means rejecting the null hypothesis when it is actually true. In statistical hypothesis testing, the event of incorrectly rejecting the null hypothesis is usually not directly verifiable because it is not generally observable whether the null hypothesis is actually true. The probability of a type I error is designated as alpha. Philippe Rocca-Serra the event of incorrectly rejecting the null hypothesis type 1 error