Which statement describes a Type II error?

• A. Rejecting a true null hypothesis.
• B. Failing to reject a false null hypothesis.
• C. Rejecting a false null hypothesis.
• D. Failing to reject a true null hypothesis.

Answer: (B)

The concept being tested is the idea of errors you can make when you decide whether or not to reject the null hypothesis. A Type II error happens when the null hypothesis is actually false, but you fail to reject it. In plain terms, there’s a real effect or difference, but your study doesn’t provide enough evidence to declare it significant, so you conclude there isn’t an effect. That’s why the statement describing failing to reject a false null hypothesis is the correct description.

To place it in context, rejecting a true null hypothesis would be a Type I error (a false alarm). Rejecting a false null hypothesis is simply correctly detecting the effect. Failing to reject a true null hypothesis is a correct non-error decision.