Question 44 • Probability and Statistics with Applications Honors Sem-1-FL-1210300 (2024-2025)
A new cream was developed to reduce the irritation caused by poison ivy. To test the effectiveness, researchers put an ad online asking for volunteers to participate in the study. One hundred subjects replied and were informed that one group would receive the new cream and the other would receive a cream with no active ingredient. All 100 subjects were exposed to poison ivy. Fifty were then assigned to the group with the new cream, and 50 were assigned to the group with the cream with no active ingredient. After three days, technicians recorded the subjects’ level of irritation.
Answer
A
This experiment should be single blind. The subjects will not know which treatment they are receiving to control for the placebo effect, but the technicians need to know which group received the new cream.
B
This experiment should be double blind. Neither the subject nor the technician knows which group is receiving the new cream to control for the placebo effect, and the response measured is not affected.
C
This experiment should be single blind. The subjects know which treatment they are receiving but the technicians do not know which group received the new cream, so the response being measured is not affected.
D
This experiment should not use blinding. It is unethical for the subjects not to know which treatment they are receiving, placebo or new cream, and for the technicians not to know which group received which treatment.
Explanation
Use a double-blind design: neither the subjects nor the technicians recording irritation should know who received the active cream. Keeping subjects unaware helps control the placebo effect, while keeping technicians unaware reduces the chance that their expectations influence how they assess irritation. The subjects can still be informed that they may receive either cream, so blinding does not require hiding that information from them.
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