The correct answer is (E).
(E) Flaw
Step 1: Identify the Question Type
The question directly asks for the flaw in the pharmacist's argument. Look for a reason why the evidence doesn't adequately back up the conclusion.
Step 2: Untangle the Stimulus
The pharmacist's argument is based on a study of insomnia patients whose condition improves after ingesting melatonin, a hormone usually produced by the pineal gland. The pharmacist uses this study to conclude (indicated by the Keyword [ t ] hus ) that the pineal gland produces less melatonin as we grow older.
Step 3: Make a Prediction
The argument seems nice. After all, if melatonin helped the patients, then their bodies probably weren't producing an adequate amount of melatonin. However, the patients are all relatively older and all suffer from insomnia, a rather convenient demographic for the pharmacist. Unfortunately, without comparison to other people (i.e., younger people and/or those without insomnia), it's hard to tell if this is normal for people in general or just unique to these individuals. The correct answer will point out this use of an unvaried study group.
Step 4: Evaluate the Answer Choices
(E) is a match. The sample used (older people with insomnia) is not exactly representative of people in general.
(A) is a Distortion and not a flaw. In the study, an action (ingesting melatonin) does have an effect (reduces insomnia). However, it would be perfectly reasonable to say that ingesting melatonin was intended to reduce insomnia. Even so, that wasn't the author's point.
(B) is a Distortion. While the manufacturers of the melatonin supplements may have an incentive for people to use their product, their claim is not flawed just because the manufacturers have that incentive. Instead, their claim was made on factual data, but alas that data was not representativeÑtherein lies the flaw.
(C) is wrong because every term is used consistently throughout the argument.
(D) is a Distortion. The only cause-and-effect relationship suggested here is that ingesting melatonin causes insomnia symptoms to subside. However, the author does not confuse this relationship, and it makes no sense that reduced insomnia would cause patients to start ingesting melatonin.
