Type I vs Type II error
MCAT glossary · Biological & Biochemical Foundations of Living Systems
Definition
Type I (α): rejecting true null (false positive); Type II (β): failing to reject false null (false negative); power = 1 - β.
Type I vs Type II error in plain English
When you run a test to decide if an effect is real, there are two ways to be wrong, and this names them. A Type I error (false positive) is crying wolf — you announce an effect that isn't actually there; its chance is called α, and it's the risk you're accepting when you 'reject the null hypothesis' (the boring assumption that nothing is going on). A Type II error (false negative) is the opposite — a real effect exists but your test misses it, with probability β. 'Power,' equal to 1 - β, is your test's ability to actually catch a real effect when there is one, like a smoke detector sensitive enough to go off for a genuine fire.
Learn these first
Sign up free: all 171 MCAT terms as flashcards, plus practice questions with full explanations →
Related MCAT terms
MCAT practice questions · MCAT flashcards · MCAT study guide