Test Error Types

Definition

Suppose

• $H_0$ : Null hypothesis
• $H_1$ : Alternative hypothesis

Then

• We say a Type I error occurs if $H_0$ is rejected when $H_0$ is true
• We say a Type II error occurs if $H_0$ is accepted when $H_1$ is true

Notes

	True state
Decision	$H_0$ is True	$H_1$ is True
Reject $H_0$	Type I Error	Correct Decision
Accept $H_0$	Correct Decision	Type II Error