What are the limitations of the extreme age group design? ANSWER:

The extreme age group design (assessing a group of 20-year-olds and a group of 80- year-olds at one point in time using the same measures) is problematic in three ways. First, the samples are not representative, and the findings may not generalize, except to people who have characteristics similar to those included in the study. Second, age is better conceptualized as a continuous category, not as old and young. Finally, the measures and terms may not mean the same things to both groups. Hence, there are issues with reliability and validity of the measures used with each cohort.