#18 - Pharmacist: A large study of people aged 65-81

[Administrator]

Complete Question Explanation

Flaw in the Reasoning. The correct answer choice is (E).

Any time you are faced with a stimulus that involves conclusions drawn from a study or survey, you should be alert to potential problems with the study and prepared for a Flaw question about those problems. Problems can include failing to use good scientific methods, such as having a control group to eliminate possible alternate explanations for observed results, problems with the way the data is interpreted, and, very commonly, problems based on unrepresentative samples. If the sample group is very narrowly defined, it would be improper to draw conclusions about anyone or anything that is not in the defined group. That flaw is on clear display here, as the group studied is limited to people in a certain age range (65-81) AND also to people that age who suffer from insomnia. Without looking at people in other age ranges and also at people without insomnia, the very broad conclusion about people in general just cannot be supported. Look for an answer that points out the unrepresentative sample in this study.

Answer choice (A): The stimulus isn't about cause and effect, nor is it about intentions (does the pineal gland intend to produce less melatonin as it ages and to cause insomnia?) While some mention is made of causality (melatonin alleviates some symptoms), the argument is not itself about that causal relationship, but about a change in people as they age.

Answer choice (B): There is no reason to suspect bias on the part of the pharmacist in this argument. While we might be suspicious of the folks who manufacture melatonin supplements, at no point did the argument rely on their position. The author only relied on the results of the study.

Answer choice (C): A common wrong answer, you should only consider the "shifting use of a term" answer if you can 1) identify the term at issue and 2) identify the two different definitions used in the course of the argument. Here there is no term that changes meaning, so this answer is a loser.

Answer choice (D): Another causal answer choice for an argument that is not really about cause and effect, but about drawing broad conclusions based on a study of a very narrow group of patients. Don't let the presence of some causal claims fool you - this argument is not "A and B are correlated, therefore A causes B," so it is not a causal argument and does not contain a causal flaw.

Answer choice (E): This is the correct answer choice. A perfect answer to match our prephrase, and if we didn't allow ourselves to fall into the trap of one of the causal answers this should be an easy one to select when we get to it.As discussed above, the group studied is too narrow because it does not include people of younger ages and because it only looked at people with insomnia.

[15veries]

Hi,
It says "unrepresentatitve" but in what sense?
2 thoughts,
1) It only ivnestigated 65-81 ppl, so they are already aged. But the conclusion says "as it ages"
2) The sample group already have insomnia, but the conclusion is about general people including those who do not suffer from insomnia.

In which sense does this answer say "unrepresentative?"

[Adam Tyson]

Thanks for the question, 15veries (may I call you 15?), and thanks for the insight into your thought process. That's very helpful.

My short answer to your analysis is "both" - the sample is unrepresentative (of people generally, or perhaps of pineal glands generally) both because we did not look at younger people, either with or without insomnia, to see what was going on with their melatonin levels, and also because we only looked at people with insomnia. What if older people like those in the study but without insomnia have normal melatonin levels? That would really hurt the claim that the pineal gland produces less as it ages.

So, this argument has both problems, and they are both about an unrepresentative sample. I can't draw conclusions about all people if I only study those with insomnia, and I can't draw conclusions about changes with age unless I look at groups at several age levels. This study didn't even compare the youngest people in the study (65-year-olds) to the eldest in the study (81-year-olds), so for all I know the older ones had MORE melatonin than the younger ones!

Don't get caught worrying about which way they meant - once you know that it is about the sample, just go with that. Usually it will be in one obvious way, but it can be a multi-layered problem, like here, and getting caught up in the layers will only slow you down.

Nice job!

[taylorharris24]

Hi,
i'm confused how D is wrong. I thought it was confusing the effect, the pineal gland producing less melatonin, with the cause, insommia. When I read it my prephrase was that it ignores that the study was only conducted on people who have insomnia, which would be a direct cause to the pineal gland producing less melatonin. I thought E might be correct too but I thought D was stronger. I probably held to my prephrase too strongly, but can you show me how it was incorrect?

Thanks in advance.

[Rachael Wilkenfeld]

Hi Taylor,

I think you may be confused as to the different claims. The manufacturer claims that the body produces less melatonin as it ages. That's separate from the causal portion of the stimulus, which discusses a recent study. The study showed that the melatonin caused an alleviation of insomnia symptoms. That's consistent with the rest of the information in the stimulus, and at no point does the author attempt to say that the alleviation of the insomnia symptoms somehow caused the melatonin. That would be what we'd need for answer choice (D) to be correct.

The big problem though, is that the sample we have is unrepresentative of the population as a whole. We don't know that melatonin naturally produced decreases with age, because we don't have young people for comparison. We also don't have examples of elderly folks without insomnia, which we would need to see as well. Otherwise, it could be the case that our sample population has NEVER really produced sufficient melatonin, or has always had insomnia. That would hurt the conclusion that melatonin production decreases with age. That flaw is well described in answer choice (E).

Hope that helps!
Rachael

[medialaw111516]

I was torn between B & D, but thought the sample was representative and that the claims made by manufacturers who benefit from older people thinking they need melatonin would make them biased?

[Paul Marsh]

Hi medialaw! The sample here is unrepresentative because it doesn't provide any data to show that melatonin production decreases with age.

Consider the following two arguments:

1) A large study of octogenarians showed that 50% of them snore heavily. Therefore, heavy snoring increases with age.

2) A large study of adults of all ages showed that 10% of young adults snored heavily, while 50% of octogenarians did. Therefore, heavy snoring increases with age.

The first argument is significantly flawed compared to the second, because there is no sample of younger adults upon which to base that conclusion! Maybe 50% of all adults snore heavily, and snoring doesn't actually increase with age at all.

The argument in the stimulus is flawed for the exact same reason - there is no sample of younger people and their melatonin production, which we would need to form the conclusion that the argument is making. That is why (E) is the right answer.

In addition to (E) being the major flaw here, we can rule out Answer Choice (B) because the argument is not relying upon the opinions of individuals who are likely to be biased. As you pointed out, it's true that the manufacturers are likely to be biased parties. However, the argument is not relying on their opinion! The argument's conclusion is agreeing with their opinion, but the conclusion is based entirely on one premise: the study. The manufacturers' opinion is NOT a premise, it just happens to be something that the conclusion aligns with. Now let's say the argument read something like "Manufacturers of melatonin claim that the pineal gland produces less melatonin as it ages. Therefore, older people likely produce less melatonin." In that case, the argument is relying on the opinion of biased individuals, since the manufacturers' opinion is the main premise of the argument. So (B) would be a correct answer in that case.

As it is however, (E) is the way to go. Hope that helps!

[Albertlyu]

Hi PS,

I just redid this question, on first glance, I did not even notice that the age gap of the study was too narrow to be able to render a broader conclusion. But I think this argument contains another flaw: just because some substance can fix a medical condition does not mean that medical condition was caused by the lacking of that substance. that is why I picked D. However, upon review I could not match my analysis with the answer choice. So may I ask if there is a causal flaw in the argument or have I just got it all wrong?

thanks.

Albert

[Robert Carroll]

Albert,

I think your analysis is reasonable - even if melatonin causes the condition to disappear, that doesn't mean the condition was caused by a lack of melatonin. The issue is that answer choice (D) is about switching cause and effect. In the author's view, perhaps the cause is lack of melatonin and the effect is insomnia? Then, in order for answer choice (D) to be correct, insomnia would have to be the cause of a lack of melatonin. That is not what the argument is doing, so that's not correct.

Robert Carroll

[Albertlyu]

got it, thanks Robert!