A psychologist first conducted a study on helping behavior with a sample of college undergraduates. This psychologist then replicated the study using the same procedure with a different participant sample. If similar results were obtained with both samples, this experimenter has demonstrated .

External validity

Explanation:

External validity means that the results of the study can be generalized to other conditions, people, stimuli, and time. Therefore, replication is essential in experimental research, meaning that studies are usually conducted with different subject populations or in different settings and then have the same results. Thus, the conclusion of the researchers can be generalized to a larger population.

C; skin, is the answer!