Logical reasoning PrepTest 103 · Section 1 · Question 8

Question prompt

Based on data collected Remaining source text redacted.
Why the credited answer is right

Credited answer: E

The notes below walk through why it fits the stem and how to eliminate the rest.

Argument or Facts

Argument

Valid or Flawed

Flawed

Question Type

Strengthen with Necessary Premise Questions

Stimulus Summary

People whose weights fall within the life insurance ranges live longer than those who don’t, so people outside that range can live longer by getting their weight inside the range.

Answer Anticipation

A given action will have a certain effect? That’s causality, my friends, and so we should start by thinking about a potential Correlation/Causation flaw. Here, the conclusion states that modifying your weight to fall in a certain range would increase overall life expectancy. That’s saying that falling in that weight range is a cause of longevity. What’s this based on? Looking at those who fall in that weight range and seeing that they live longer. That’s a correlation, as the results of most studies are. So we have a Correlation/Causation flaw. How does that flaw intersect with Necessary Premise questions? In general, we’re looking for answers that rule out alternative causes. That includes reversed causality, or another cause that results in both correlated phenomena. Let’s look for an answer that does that!

Answer choices

  1. A
    Some people would be Remaining source text redacted.
    Why choice A is not credited
    The conclusion is that a given change would have an effect if carried out, which doesn’t assume that people will actually make the change.
  2. B
    Life insurance companies intended Remaining source text redacted.
    Why choice B is not credited
    The intent of the life insurance companies is out of scope of an argument about what effect certain changes would have on longevity.
  3. C
    The tables include data Remaining source text redacted.
    Why choice C is not credited
    The argument is about life expectancy and tendencies, not absolute rules. As such, even if some people who lose the weight end up dying early because of an accident, their life expectancy before that happened wouldn’t change! (And, the way that the insurance tables work, those accidents would already have been factored in, but you don’t need to know that to rule this answer out.)
  4. D
    Holders of life insurance Remaining source text redacted.
    Why choice D is not credited
    The conclusion states that the effect of modifying your weight would improve your life expectancy, but not to a certain level. The argument does assume that the effect of weight on the longevity of life insurance policy holders is representative, but this answer doesn’t address that gap.
  5. E
    People's efforts to modify Remaining source text redacted.
    Why choice E matches the stem
    This answer doesn’t fall into our expected pattern of introducing an alternative cause, but it does fit another pattern on the LSAT. When an argument brings up a change, it usually ignores other potential consequences. Even if weight and longevity are related, and as such modifying your weight to fall in the “healthy” range would increase longevity, that modification might also hurt your health in some way that would decrease life expectancy. This answer rules that possibility out, which is necessary for the conclusion to hold, making this a necessary premise.

What this tests

Question analytics

Based on historical answer selection rates for this question.

Answer choice distribution

  1. A 5%
  2. B 8%
  3. C 3%
  4. D 7%
  5. E Credited 78%

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