Question: Suppose you wanted to know if men or women students spend more money on clothes. You consider two different plans for carrying out an observational study:
Plan 1: Ask the participants how much they spent on clothes during the last 3 months; then compare the men and women.
Plan 2: Ask the participants to keep a diary in which they record their clothing expenditures for the next 3 months; then compare the men and women.
a. Which of these plans is a retrospective study? What term is used for the other plan?
b. Give one disadvantage of each plan.