_____ Involve Using an Experimental Group That Has Already Been

Multiple Choice

_____ involve using an experimental group that has already been exposed to a suspected causal agent, finding a controlled group that has not been exposed to the agent but matches the experimental group in all other relevant respects, and then tracking the two groups over time to determine a cause-and-effect relationship.

A) Nonrandomized prospective studies
B) Randomized double-blind trials
C) Nonrandomized retrospective studies
D) Randomized block designs