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October 25, 2018

Common LSAT Question Types: Must Be True vs. Weaken

Common LSAT Question Types: Must Be True vs. Weaken

When approaching Logical Reasoning on the LSAT, I think most students clearly recognize the importance of (1) understanding the unique properties of individual question types, and (2) having dedicated strategies to consistently apply when faced with a particular type of question. That is the value in knowing how to recognize, say, a Parallel Reasoning question, and then understanding the proper approach to take when attacking Parallel Reasoning.

Make no mistake about it: the ability to distinguish different types of questions from one another is crucial to success on test day. However, as important as it is to identify what makes one question type different from another, it is also extremely important to understand the similarities between question types, and that is what I want to discuss here.

Must Be True vs. Weaken

One of the most surprising relationships on the LSAT exists between Must be True questions and Weaken questions. I say their similarities are “surprising” because at first glance these two questions seem to be presenting almost completely opposing tasks: Must be True questions ask you to use stimulus information to prove that an answer choice is true, whereas Weaken questions ask you to use an answer choice to attack the argumentation in the stimulus, essentially showing that the conclusion is not necessarily true. But consider both question types from a broader, argumentation-based viewpoint, and some striking consistencies begin to emerge.

Must Be True

Think about what makes an answer choice incorrect in a Must be True question. Individually it can be any one of a number of errors—new information not addressed in the stimulus, information that is stronger or more exaggerated than the support given in the stimulus, an improper comparison of stimulus elements where the relationship cannot be definitively known, etc.—but collectively they can all be summed up as “information that is not guaranteed based on the stimulus.” In other words, wrong answers in MBT are all just invalid conclusions; we cannot know that an answer choice is 100% certain, so in LSAT terms it is not true.

Weaken

Now let’s look at things from a Weaken perspective. What is it about an argument in a Weaken stimulus that allows it to be attacked? Well, individually, arguments can be vulnerable for a number of reasons—an author relies upon incomplete evidence or draws a conclusion containing new information, the conclusion is qualified/limited in some way that leaves it open to attack, the author attempts to compare two or more items whose relationship cannot be clearly known, etc.—but collectively, vulnerable (or invalid) arguments are ones where the author’s conclusion is not guaranteed based on the premise information. Exceptions to the conclusion could exist, and the correct answer in Weaken simply provides evidence of the possibility of some exception.

Hopefully as you consider the previous two paragraphs you’ll notice the rather remarkable degree of similarity between incorrect answer choices in Must be True questions, and conclusions as given in Weaken stimuli. In all cases some element within them cannot be known with certainty, and thus they are invalid. And this consistency becomes even more useful/powerful once you realize that the reasons that they cannot be completely known are often the same, as I’ve tried to illustrate with the specific errors listed above.

Adapt Your Preparation

This realization should serve a number of different purposes as you continue to prepare. For one, you should begin to treat any and all argumentation on the LSAT the same way that you treat Must be True answer choices: with skepticism. Always ask, “Why?” when presented with an author’s opinion—“Why does the author believe this? Why should I believe this?”—and do not accept that opinion until you are completely satisfied that the evidence provided shows that the conclusion must occur in the way the author believes that it will. When you encounter a questionable conclusion, and you understand exactly why it is uncertain, you are in the perfect position to manipulate that argument!

And secondly, you should find that as your abilities improve in one area, that success will translate into improvements in other areas as well. As you become more adept at eliminating Must be True answers, you should find that you are also better at recognizing vulnerabilities in argumentation and choosing answers that exploit those vulnerabilities (correct answers in Weaken), or eliminate those vulnerabilities (correct answers in Strengthen, Assumption, and Justify). And vice versa: the more skilled you becoming at spotting questionable arguments, the more skilled you become at spotting incorrect Must be True answers.

So while you work hard to correctly identify and attack each individual question type, don’t overlook the benefits gained by understanding the consistencies they share.

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Posted by Jon Denning / Logical Reasoning, LSAT Prep / Logical Reasoning, LSAT Prep Leave a Comment

  • Raini Edwards
    December 16, 2018 at 12:56am

    This message for Mr. John Denning.
    Good evening its saturday night December 15th, and have a question
    please respectfully Mr. Denning when your time permits to respnd i will greatly appreciate.

    The upcomimg Jan. 2019 and Mar. 2019 LSAT, I need to know what the score was from Nov. 17th test and how will this
    effect the future scores for the 2019 LSAT Jan and Mar 2019 ?

    It seems the scoring is becoming more and more narrow therefore, it will be increasingly difficult to get 150 score passing.
    I need to know how many questions can I get wrong and still score a 160 and also a 150 too need to understand, since the scoring is becoming more and more, of a challenge.

    Thank you, Raini

  • Jon Denning
    December 17, 2018 at 11:28pm

    Hi Raini – thanks for posting! Are you asking about the November LSAT’s scoring scale and what it might mean for the scales on the next few tests? If so, let me answer in two parts!

    First, the November scale isn’t publicly available yet because that test hasn’t been released for sale by LSAC, so I can’t post the whole thing. But I can give you a few raw score conversion points and let you compare them to other tests here: https://www.powerscore.com/lsat/help/correct_targeted.cfm

    There ended up only being 99 scored questions in November, out of which you needed 89 right to get a 170. So strictly speaking you could miss 11 questions, provided one of them was question 27 in RC (that’s the one they removed). Otherwise you could only miss 10. That’s a pretty strict curve historically, but totally in line with what we’ve seen the past few years. For a 160 you needed 73 right, which is actually on the loose/soft side compared to the past several years, and a 150 required 55 correct answers: that matches 4 of the last 6 tests exactly in terms of raw score needed for that target (150). So again, standard.

    The second part of this answer is tougher, because one test doesn’t tell you much about the next! Consider the June 2017 exam where you could only miss 9 to get a 170! That’s the tightest scale in the last decade at the upper end…and what preceded it? A -12 and -11. What followed it? A -11 and -12.

    Point being that you can track overall, years-long trends, but doing it on a test to test basis is far less helpful because outliers exist and things change from one to the next. As an example, a 99 scored question test hasn’t happened since June 2010, so more than 8 years passed before it happened again in November.

    That said, what I think will happen in January and/or March, if they’re new tests and not something old that gets reused, is we’ll see the same trends of late: between -10 and -12 for 170, etc.

    Finally, and unfortunately, we’ll also never know! Jan and March are both nondisclosed tests, meaning no one gets a copy (not the questions, answers, or curve)…so even if I predicted a -12 it’d only ever be a guess, and impossible to confirm.

    So worry less about curves and more about content! Master everything from 2016-2018 and you should be in great shape no matter what 🙂

About Jon Denning

Jon Denning is PowerScore's Vice President and oversees product creation and instructor training for all of the exam services PowerScore offers. He is also a Senior Instructor with 99th percentile scores on the LSAT, GMAT, GRE, SAT, and ACT.

Jon is widely regarded as one of the world's foremost authorities on LSAT preparation, and for the past decade has assisted thousands of students in the law school admissions process. He has also created/co-created a number of PowerScore’s LSAT courses and publications, including the Reading Comprehension Bible, the In Person, Live Online, and On Demand LSAT Courses, the Advanced Logic Games Course, the Advanced Logical Reasoning Course, and a number of books in PowerScore’s popular LSAT Deconstructed Series.

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