Which of the following is a drawback of longitudinal studies? a. Participants may drop out of the study over time. b. They are subject to cohort effects. c. They have limited generalizability. d. They cannot be used to discuss causality.

Answer:a. Participants may drop out of the study over time. b. They are subject to cohort effects.

Explanation: Participants Tend to Drop Out Over Time

When participants drop out of a study this is referred to as selective attrition. Since longitudinal studies may take a long time from months to years participants may drop out for various reasons. Some may no longer live in the area where the study is conducted or just don't feel motivated to continue anymore. Some may even pass away before the complete years of the study.

When the final group of the study no longer resemble the original sample this may have an impact on the validity of the study. Validity means the test actual measures what it claims to measure

Cohort effects refers to variations that occurs over time, within the group that shares similar characteristics such as year of birth or years of specific exposure. Over time people who share similar characteristics may begin to show variations for many reasons such as change of lifestyle amongst individuals.