In a matched pairs design, what is the first step before allocating participants to different conditions?

In a matched pairs design, the first step typically involves pre-testing participants for a variable that is relevant to the study's outcome. This process is critical because it allows researchers to identify the key characteristics or variables that might affect the dependent variable being measured. By assessing these characteristics ahead of time, such as intelligence or a specific personality trait, researchers can then match participants who are similar in those key aspects. This matching helps to control for potential confounding variables, ensuring that any differences observed in the dependent variable after applying the different conditions can be more confidently attributed to the independent variable rather than inherent differences between participants. Consequently, this enhances the internal validity of the study and allows for a clearer interpretation of results.

The other options entail steps that either occur after this initial matching process or do not contribute directly to creating matched pairs, thereby making them less relevant in the context of the first step in a matched pairs design.