Question

When is the most appropriate time to calculate power?

• A. after you rejected the null in an experiment
• B. after you rejected the null in a study
• C. when designing an experiment
• D. a or b

Your friends calculate a Cohen’s d of -0.45, but they are unsure of how to interpret it. What would you tell them?

• A. They have found a small effect.
• B. They have found a medium effect.
• C. They have found a large effect.
• D. They have done something wrong.

You are asked to provide the 99% confidence interval as an estimate of a population mean. As your sample gets larger this confidence interval will ________________.

• A. become wider
• B. become more normal
• C. stay the same
• D. become narrower

Answer 1

Answer:-

Power is the probability that a test correctly rejects a false null hypothesis. Hence both statements (a) & (b) are correct.

Answer(1)  a or b

Hence option (D) is correct choice.

(2) Cohen’s d of -0.45

Cohen's d is a measure of the magnitude of effect and cannot be negative. That is,

They have done something wrong.

Hence option (D) is correct choice.

(3) Increasing the sample size decreases the width of confidence intervals, because it decreases the standard error. That is,

As your sample gets larger this confidence interval will become narrower.