Why give the control group a sugar pill?
A team is testing a new painkiller. Someone proposes the simplest design: give the drug to one group, give the other group nothing, and compare reported pain.
Explain why a good trial instead gives the control group an identical dummy pill, and why neither patients nor evaluators should know who got which.
Your answer
This one is open-ended. Work it through, then check your reasoning against the full solution.