Logical ReasoningDifficulty: Medium

PT141 S4 Q18 Explanation

So far this summer

A free, expert breakdown of this official LSAT Logical Reasoning question.

TopicsParallel Flaw

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Stimulus

So far this summer there has been no rain in the valley. But usually a few inches of rain fall there each summer. Since only one week of summer is left, valley within the next week.

What this question is testing

Parallel Flaw

Your task

Break the argument into its conclusion and evidence, then do exactly what the question stem asks with that structure.

Common trap

Answers that sound relevant to the topic but don't connect to the argument's actual reasoning.

Winning move

Predict what a right answer must do, then test each choice against the conclusion-evidence gap.

Reading along? Open the full official question in LawHub — we show a fragment here and keep the reasoning in our own words.

The question
18.

The flawed pattern of reasoning in the argument above is most similar to that in which one of

Answer choices

  1. Weak Conclusion/Premise Match16% picked this

    Aisha has finished proofreading all but the last two pages of an issue of the journal Periodos and has encountered no errors. However, there

    The original argument played off the idea that there is usually rain by time X, so there will probably be rain in the remaining time leading up to time X. This argument is saying there are sometimes a few errors, so there may be errors we find before we're done. Probably/usually are of a different strength than sometimes/may (the former means it's likely, the latter means it's possible). It's possible this answer would turn out to be the best available, and we would have to forgive that difference, but on a first pass we wouldn't be receptive to it.

  2. Bad Premise Match5% picked this

    There are generally few errors in an issue of the journal Periodos. Aisha has finished proofreading all but the last two pages of an

    This is fairly tempting, but to match the original we would want to hear, "There usually are a few errors. We haven't found any so far, so there will probably be some in the remaining pages." In the original argument, there is a mismatch between the usual (there's usually a few inches of rain each summer) and the observed (there hasn't been any rain so far). In this argument, there isn't a mismatch. The usual (there are usually few errors) and the observed (there haven't been errors so far) are aligned.

  3. Correct72% picked this

    On average, there are a few errors in an issue of the journal Periodos. Aisha has finished proofreading all but the last two pages

    Why this is right

    There is usually a few inches of rain each summer. There are a few errors in every issue, on average. One week left, and no rain so far this summer. Two pages left, and no errors so far. Thus, it will probably rain in the next week. Thus, there will probably be errors in the last two pages.

    Skill tested: Parallel Flaw · how this choice captures the argument's function is the move to repeat next time.

  4. Bad Premise Match4% picked this

    Aisha has proofread several issues of the journal Periodos and has encountered no errors. But there are seldom any errors in an issue of

    Just like (B), there's no mismatch here between the usual and the observed. The original argument was saying, "Since something we usually see occur hasn't yet occurred, it will probably occur soon". This argument is saying, "We usually don't see errors in this journal. And Aisha hasn't seen errors in this journal".

  5. Bad Conclusion Match2% picked this

    There usually are errors in each issue of the journal Periodos. Since Aisha has finished proofreading the latest issue of this journal and has

    The conclusion has to be related to the "usual" thing we see. In the original argument, there usually is rain during the summer, and so the conclusion is predicting there will probably be rain (during the remaining week of summer). Here, there are usually errors in each issue of the journal, so the conclusion should be predicting that there will be an error in the remaining part of the journal. Instead, the conclusion is saying that Aisha probably messed up.

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