If a researcher uses a method to prevent any systematic relationship between a factor and the group, what process is he employing?

The correct answer is randomization because this process ensures that participants are assigned to different groups in a way that eliminates bias and prevents any systematic relationship between the factor being tested and the groups. By randomly assigning participants, researchers can spread out any known or unknown factors that could influence the outcome, thereby increasing the internal validity of the study.

Randomization helps ensure that the groups are equivalent at the start of the experiment, making any differences in outcomes more likely attributable to the independent variable rather than other confounding factors. This is a fundamental principle in experimental research, as it allows for more accurate comparisons and conclusions.

Matching, selection, and grouping refer to different methodologies that may be employed in research but do not specifically aim to prevent systematic relationships through random assignment. Matching is often used to pair participants across groups based on certain characteristics, which does not eliminate relationships but rather controls for them. Selection refers to how participants are chosen for the study, and grouping is a more general term that does not specifically pertain to the randomization process.