What is a notable disadvantage of repeated measures design regarding order effects?

In a repeated measures design, the same participants are used in all conditions of an experiment. This approach can produce order effects, which occur when the sequence in which treatments or conditions are administered impacts the results. For instance, if participants take a task multiple times, they may become fatigued or bored, which can influence their performance.

When participants are fatigued, their ability to perform tasks may decrease over time, leading to results that do not accurately reflect their true capabilities or the effects of the independent variable. This fatigue can distort the findings, making it challenging to determine if changes in the dependent variable are due to the experimental manipulation or the participants' declining performance over repeated trials.

The other options relate to aspects that are not directly tied to the notable disadvantage of order effects in a repeated measures design. Random sampling, sample size, and the concept of a control group are important considerations for experimental validity, but they do not specifically address the complications caused by order effects, particularly fatigue.