LR Question 17 Explanation, by LSATHacks
QUESTION TEXT: A 24-year study of 1,500 adults showed that those…
QUESTION TYPE: Paradox – Exception
PARADOX: Beta-carotene in foods was associated with less cancer and heart disease. Beta-carotene supplements had no such association.
ANALYSIS: Your main job on “EXCEPT” question is not to forget that they're “EXCEPT” questions.
Beyond that, just open your mind to ways that the paradox could be resolved. What are differences between foods and supplements? Here are some I brainstormed:
- Supplements are synthetic
- Supplements have the wrong dose
- Supplements don't absorb well
- There are other compounds in foods that help
I don't know if these will all be in the answers. But I think I'll go through the answers faster for having taken a few seconds to think about possibilities.
Here's a tip for prephrasing. I often hear students say “I can't prephrase!”. Pretend someone was paying you $50 if you could think of an explanation. Or $50 to find a reason an argument was wrong. You'd think a bit harder then, wouldn't you?
___________
- This is my third explanation from the analysis section.
- This is something I didn't think of, but it's a relevant difference between the two studies. The supplement study only lasted 12 years.
- This is my fourth explanation from the analysis section.
- CORRECT. This actually shows the study was well performed. You're supposed to have a control group that takes a placebo.
- This is a complex answer, but it says: if you eat beta-carotene, you smoke less. And we know from outside knowledge that smoking causes cancer and heart disease. So this shows an alternate cause: less smoking in the beta-carotene group.
(You can assume facts that no one would disagree with. That's called a “warranted assumption”.)
Recap: The question begins with “A 24-year study of 1,500 adults”. It is a Paradox – Exception question. To practice more Paradox – Exception questions, have a look at the LSAT Questions by Type page.
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I chose D as the correct answer because it was the only one left after elimination. I don’t feel that any outside knowledge was necessary. Please correct me if I am wrong.
A) shows why study 1 shows an effect of beta-carotene (food vs. supplement) and thus resolves the discrepancy.
B) shows how time difference could be masking the effect of beta-carotene, so study B shows no effect since it is shorter, thus resolves the discrepancy.
C) similar to A (a bit far-fetched but works) shows why beta-carotene from food is more effective and thus resolves the discrepancy.
D) doesn’t do anything (unless I am missing some logical thinking here)
E) shows how a confounding variable (smoking) in the study could be showing us an effect of beta-carotene in the first study, thus resolves the discrepancy.
D is only one that appears to not resolve….actually I am not sure what it does. For the sake of correct answer, it doesn’t matter.
Thanks for all the great explanations and being a great study source.
Is it fair to say that in order to have answered this correctly, I would’ve had to understand with outside knowledge that placebos are necessary for a study to be performed well? Without this knowledge, could I have come to find this answer to be correct some other way?
Thanks!
Actually, yes. They never say this but a bunch of questions require you to have common knowledge of study design.
It’s mostly logic anyway. Like you can only conclude a change produced an effect if you can know what would have happened without the change.
The LSAT in general requires you to assume:
* Common sense stuff that everyone would agree with is true
* Basic scientific knowledge is true
* Study design is true
I have nothing major to add except that there is a typo in the last paragraph of the analysis. Specifically: “I often here students say” (here should be hear). Not trying to be annoying, just pointing it out. The information contained on this site is incredible. Thank you so much!
Thanks for catching that Mo, the page has been updated. And it’s so great to hear that you’ve gotten so much from the site!