Because the Participants Who Drop Out of a Longitudinal Study

Multiple Choice

Because the participants who drop out of a longitudinal study are likely to be different in some ways from those who remain until the end of the study

A) the conclusions drawn from longitudinal studies are seldom reliable.
B) the sample that is initially representative becomes increasingly biased over time.
C) there will be a cohort effect upon the final results.
D) attrition will make the sample more representative over time.