Power of a study is the probability of correctly rejecting a false null hypothesis. This corresponds to avoiding which type of error?

• A. Type I error
• B. Alpha error
• C. Falsely concluding a treatment is beneficial when it is not
• D. Type II error

Answer: (D)

Power is about detecting real effects. It is the probability that a study will reject the null hypothesis when the null is actually false. The error that this aims to avoid is failing to reject a false null hypothesis, known as a Type II error. So higher power means a lower chance of missing a true effect. The phrase about concluding a treatment is beneficial when it is not describes a false positive, which is a Type I error, not what power addresses.