Why Is It Important to Make Sure That Different Participant

Multiple Choice

Why is it important to make sure that different participant groups are roughly equivalent in terms of personal characteristics (e.g., age, gender) before any independent variable is introduced?

A) Because it is important to treat all research participants equally so that they feel that they are not being manipulated.
B) Because research ethics forbid any experiment to take place when the participant groups are fundamentally different from each other.
C) So that no major differences between the groups unduly bias the results of the experiment.
D) Because it threatens the integrity of a within-group experimental design.