A researcher wants to examine the changes in the stability of friendship between first and third grade. Should the researcher use a cross-sectional or a longitudinal design? Explain your choice. Give the advantages and disadvantages of each design

What will be an ideal response?

A good answer will be similar to the following:
A longitudinal study would involve looking at children's friendships in first grade. Later, when the same children were in third grade, researchers could see how many friendships still existed. A cross-sectional study might involve asking a group of first-graders and a group of third-graders questions about the stability of their friendships. The main advantage of a cross-sectional research design is that it can be done in a relatively short period of time and at a much lower cost than a longitudinal study. The major disadvantage is that cohort effects may be present which make it difficult to draw conclusions about developmental change. The main advantage of longitudinal research designs is that cohort effects are eliminated and actual stability and change can be studied. The major disadvantage of longitudinal studies is that they are expensive. Other disadvantages include the lack of sample constancy over the course of the study as participants drop out and the development of "test-wise" participants.