In experimental investigations, who determines the exposure of participants to factors being studied?

The investigator plays a crucial role in experimental investigations, particularly in determining the exposure of participants to the factors being studied. This responsibility involves designing the experiment, selecting the treatment conditions, and assigning participants to various groups, such as treatment and control groups. The investigator ensures that the exposure is administered consistently according to the study protocol, which is essential for collecting valid and reliable data.

In addition, the investigator's choices directly impact the study's internal validity, as they determine how well the results can be attributed to the factors being manipulated rather than to external variables. Effective control of the exposure enables the researcher to establish cause-and-effect relationships between the independent variable (the factor being studied) and the dependent variable (the outcome measured).

While the other entities mentioned have their roles, they do not determine exposure in the same way. The control group is a benchmark group that does not receive treatment and serves for comparison. Participants may have preferences or experiences that could influence their responses but do not control the exposure per the study design. A research committee may oversee ethical compliance and methodology, but it is the investigator who operationalizes the exposure within the study.