Which of the following is a serious concern when conducting a repeated-measures study?

• A. Difficulty in random assignment of participants to groups
• B. Order effects, where the sequence of conditions influences participants' responses
• C. Low statistical power because of small sample sizes
• D. Sampling bias due to recruiting only from a single location

Answer: (B)

Verified step by step guidance

1. Understand the design of a repeated-measures study: the same participants are exposed to all conditions or treatments, which means each participant serves as their own control.
2. Recognize that because participants experience multiple conditions in sequence, their responses in later conditions can be influenced by their experience in earlier ones. This is known as 'order effects.'
3. Identify common types of order effects, such as practice effects (improvement due to repetition) and fatigue effects (decline due to tiredness), which can bias the results.
4. Note that random assignment to groups is less relevant here because all participants undergo all conditions, so the main concern is controlling or counterbalancing the order of conditions to minimize order effects.
5. Conclude that among the options given, order effects are a serious concern in repeated-measures designs because they can confound the interpretation of the results if not properly managed.