Which step is part of performing a simple power calculation for a study?

• A. Estimate expected effect size
• B. Randomize participants
• C. Draft consent forms
• D. Collect data on outcomes

Answer: (A)

Power calculations determine how many participants are needed to detect an effect with a specified probability. The step that fits performing a simple power calculation is estimating the expected effect size. This matters because the size of the anticipated difference between groups largely dictates the required sample; a larger expected effect means you can use fewer participants, while a smaller expected effect means you’ll need more. When you perform the calculation you also pick a significance level and target power, and you may need information on variability or event rates, but you must start with the estimated effect size to drive the calculation. The other activities—randomizing participants, drafting consent forms, and collecting data on outcomes—are essential parts of the study but are not the calculation step itself.