Answer:
The provided statement is True.
Step-by-step explanation:
Holding a variable constant implies that there are no kind of relationship between the variables and the treatments.
Holding a participant variable constant has the double advantage:
(1) preventing the variable from becoming a confounding variable
(2) reducing variance within groups.
A confounding variable effects both the dependent and the independent variable remarking a relationship between the two.
Variation within group implies the difference caused by the individual values of each group.
Thus, the provided statement is True.