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A study is designed to investigate potential adverse effects of drug X. A table

ID: 2921573 • Letter: A

Question

A study is designed to investigate potential adverse effects of drug X. A table given below summarizes the outcomes. The researcher randomly assigns 204 from a group of 409 participants to take drug X. The remaining 205 subjects received placebo. Row 1 of the data table gives the numbers of participants who report experiencing adverse effects. Another variable we consider is age.

Do you observe Simpson's paradox for this dataset? Explain.

Drug X Placebo Age < 55 Age 55+ Age < 55 Age 55+ Adverse 8 22 5 16 No Effect 98 76 115 69

Explanation / Answer

The study shows that drug X has potential adverse effect of 26.67% (8/30) on age less than 55, and and 73.33% (22/30) on age 55+. Wheras, placebo has adverse effect 23.80% on age less than 55 and 76.19% on age 55+. Thus, it apparently seems that placebo has adverse effect on age 55+. Now, combining the participants for two age groups, one sees that 14.71% (30/204) has adverse effect in drug X group, and 10.24% has adverse effect on placebo group. Therefore, it appears that as a whole, drug X has adverse effect. Thus, the trend that appeared in different groups disppeared when groups are combined. Hence Simpson's paradox is apparent.