This document discusses the two types of errors that can occur when testing hypotheses: type 1 errors, which occur when rejecting the null hypothesis when it is actually true, and type 2 errors, which occur when accepting the null hypothesis when it is actually false. There are four possible outcomes when testing hypotheses: committing a type 1 error, correctly rejecting the null hypothesis, correctly accepting the null hypothesis, or committing a type 2 error.

1. Type 1 and Type 2 errors I think there is a tiger over there…

2. Null Hypothesis Alternative Hypothesis … so I postulate two hypotheses There are four ways this could turn out

3. I could reject the null hypothesis… Null Hypothesis Alternative Hypothesis … and be wrong – a Type 1 error

4. or I could accept the null hypothesis… Null Hypothesis Alternative Hypothesis … and be right

5. or I could reject the null hypothesis… Null Hypothesis Alternative Hypothesis … and be right

6. or I could accept the null hypothesis… Null Hypothesis Alternative Hypothesis … and be wrong – a very bad Type 2 error