Error that concludes that someone is not guilty, when in fact, they really are. (Ha true, but I concluded Ho). BETA
Accept an hypothesis or statement as true when it is false: Ho is false, but I conclude Ho is true. Error that concludes that someone is not guilty, when in fact, he or she really is. (accept Ho as true, beeing false, when Ha is true).
A failed alarm is a Type II error
BETA is the probabilty of error type II