To study the effects of aging,Professor Drake compares the reaction times of 60-year-olds with those of 30-year-olds.She tests all younger subjects in the morning,and all older subjects in the afternoon.She concludes that aging causes a decline in the speed of responses.This study lacks ________ because of potential ________.
A) external validity; demand characteristics
B) external validity; confounds
C) internal validity; demand characteristics
D) internal validity; confounds

Question

Quizplus · Accepted Answer

This study lacks internal validity because it is not controlling for potential confounds, such as time of day. By testing younger subjects in the morning and older subjects in the afternoon, the results could be influenced by differences in alertness or fatigue rather than age. Therefore, it is not possible to determine if the observed decline in reaction time is due to aging or another factor.

To Study the Effects of Aging,Professor Drake Compares the Reaction