Dr Cameron Decided to Combine Different Types of Variables into a Single

Dr. Cameron decided to combine different types of variables into a single category for a literature review. This decision is LEAST justifiable if the studies

A) used different types of settings, such as laboratory settings and natural settings.
B) used different types of dependent variables such as self-report and behavioral observation.
C) provided effect sizes based on different types of statistics such as the F-test and the t-test.
D) provided effect sizes based on different types of research designs such as experimental and correlational.