#22 - In 2005, an environmental group conducted a study

[Administrator]

Complete question explanation.

Flaw Question. Cause and Effect. The correct answer choice is (A).

The stimulus tells us that the sample size used in this 2005 study was too small to generate valid inferences, but then concludes that because younger participants had lower levels of toxic chemicals in their system, the ban of these chemicals was effective at reducing human exposure. The stimulus identifies the banning of PCB chemicals as the cause for reduced levels of PCB exposure (the effect of the ban).

There are likely a lot of possible cause and effect flaws that could be present here, but the most glaring flaw in the reasoning is that the author initially says this sample size was too small to draw inferences from, but concludes by doing just that. That is the answer choice we should be looking for.

Answer choice (A) - This is the correct answer. This mirrors the answer choice option we prephrased.

Answer choice (B) - The argument might have overlooked this, but that's not the flaw in the reasoning. Even if the argument didn't overlook this factor, and PCBs were the only chemicals that could be involved, the reasoning would be flawed, so this cannot be the correct answer choice.

Answer choice (C) - the level of PCBs in younger participants is support for the inference that people have reduced exposure following the ban. The issue is that this is weak support, since the sample size of the study was too small.

Answer choice (D) - To take this out of abstract terms and apply it, this answer choice would mean that the argument assumed that the PCB chemical ban was the cause of the reduced human exposure to PCB, when in reality reduced exposure to PCB chemicals could have been the cause of the ban. This is irrational, especially since the stimulus set up the timeline of the ban occuring in the 1970s and the study occuring in 2005, eliminating this possibility.

Answer choice (E) - the argument doesn't explicitly address this, but similar to answer choice (B), even if this was true the reasoning of the argument would still be flawed, so this answer choice is incorrect.

[lsatstudent]

Why is A correct? Is it because the author first says that the sample size is too small to draw a conclusion about and then proceeds to draw a conclusion?

[Dave Killoran]

Hi LSATStudent,

Thanks for the question! Yes, that is exactly correct—well done! The stimulus notes early on that "Scientifically valid inferences could not be drawn from the study because of the small sample size" but then later says that "This proves that..." These two positions contradict each other, which is the same thing as being inconsistent. Answer choice (A) describes that problem that perfectly.

Please let me know if that helps. Thanks!

[tamarisk]

I understand that A is correct, but what about D? Even though A is biggest flaw when it comes to the answers, is D considered a actual flaw of the argument or is the answer actually just plain wrong? When I try to switch the chemical exposure and banning in my head back and forth as the cause and effect based on what is written in the stimulus, it seems to be legitimate in saying that the author made that kind of error.

[Jonathan Evans]

Hi, Tamarisk,

On flaw questions, if you make an answer choice a contender, you have to match that answer choice exactly to corresponding concepts in the stimulus. To be certain that you have the answer right, there is no room for settling for "good enough." You must have an affirmative reason why the answer you choose is correct.

Take answer choice D. Isolate the concepts in the answer choice you wish to match. First what would one posit is the "something" that is the "cause of the reduction?" The only plausible match is the "regulations banning PCB." Now ask could the "regulations" be an effect of the reduction? Clearly not. There is no match, so in this case answer choice D does not describe a flaw here.

Good question. I hope this helps.

[attorneyatpaw]

I selected answer choice (D) because in my prephrase, I thought that the most glaring flaw presented in the stimulus was that it was inferring causation from a mere correlation-- aka saying that the regulation caused lower levels of PCBs in younger people when it could've been caused by something else or the causal relationship was flipped. Although I admit that the latter would be unlikely (the regulation being an effect of the reduction in PCB levels), I still think it's within the realm of possibilities.. for example, couldn't health officials/scientists have noticed somehow that lower levels of PCBs (caused by some other reason) led to improvement in public health and used that data to create a regulation banning PCBs?

I was also considering answer choice (A) because I saw that it was also a legitimate flaw in the argument, however, I felt that the causation /= correlation flaw was the most problematic of the two. The author of the stimulus recognized that the study's sample size was too small but even if the sample size had been large enough, it still wouldn't have justified the conclusion they drew regarding causation. In that case, wouldn't answer choice (D) be the best answer choice because it's a bigger flaw than the "inconsistent stance" referred to in answer choice (A)?

[Adam Tyson]

The inconsistency is a huge problem here, attorneyatpaw. The author says that you cannot draw any valid inferences due to the sample size, but then proceeds to draw an inference, completely contradicting themself on that issue. You can't have it both ways!

Yes, there is a causal problem here, and if there was an answer that described a failure to consider an alternate cause for the reduction in PCBs, or one that clearly indicated that the reduction happened before the ban, those would have been much more attractive. But D focuses on the very unlikely reversal issue, which makes little sense in this case. How could a general reduction in exposure to a toxic chemical cause a law to be passed? The way you rationalized it required telling yourself a bit of a story to make it work, about legislators noticing a connection to health. Answers that need that much help just to make sense are not good answers! The right answer is right with no help at all, and answer A is exactly that kind of answer.