LSAT Strengthen, Weaken and Sufficient Assumption Questions

If your score report shows a lot of missed Strengthen questions, look at your Weaken and Sufficient Assumption lines too. They usually move together. The three question types look different, but they test the same skill: seeing the gap between the evidence and the conclusion.

Once you can see the gap, all three get easier at the same time.

Every argument has a gap

An LSAT argument gives you evidence and a conclusion. The conclusion always claims a little more than the evidence proves. That extra piece is the gap, and almost every Strengthen, Weaken and Sufficient Assumption question is about it.

Here's an example I made up:

Students at Hillcrest who took the optional logic seminar scored higher on the final exam than students who didn't. So the seminar improves exam scores.

The evidence is a difference between two groups. The conclusion is that the seminar caused it. The gap: maybe the seminar students were different to begin with. Stronger students might be exactly the ones who sign up for an optional seminar.

Now look at what each question type does with that gap.

• Weaken widens it: Only students with the highest grades were allowed to sign up for the seminar. Now there's another explanation for the higher scores.
• Strengthen narrows it: Before the seminar began, students who signed up had the same average grades as students who didn't. That rules out the other explanation.
• Sufficient Assumption closes it: Any difference in final exam scores between the two groups was caused by the seminar. Add that, and the conclusion has to be true.

It's the same argument with the same gap. Strengthen and Weaken ask you to move the gap. Sufficient Assumption asks you to close it.

Why students miss all three

When I go through these misses with a student, the same few habits show up.

• They read the answers before finding the gap. Then every answer that sounds related to the topic looks good.
• They attack the evidence. On Weaken questions the evidence is treated as true, so the right answer goes after the link between the evidence and the conclusion, not the facts themselves.
• They pick an answer that helps but doesn't guarantee. On Sufficient Assumption, "makes the argument better" isn't enough. If the conclusion could still be false with the answer added, it's wrong.
• They pick an answer that restates the conclusion in different words. That doesn't strengthen anything.

How to drill the gap

1. Write the gap before you look at the answers, in one sentence: "The argument assumes ___." If you can't fill in the blank, reread the argument, not the choices.
2. Predict the direction. Weaken: what would make the gap bigger? Strengthen: what would make it smaller? Sufficient Assumption: what would close it?
3. On Sufficient Assumption, find the new idea. The conclusion usually contains a term the evidence never mentions. The right answer connects that term to the evidence.
4. Drill each type slowly first. Do five to eight questions of one type, untimed, and explain every wrong answer in one sentence.
5. Then mix the three types together. Since they're one skill, mixing them is the real test. You should be finding the same gap and only changing what you do with it.
6. Review by gap, not by question type. For each miss, write down which part of the gap you didn't see. After a week you'll notice you keep missing the same kinds of gaps: an alternative cause, a sample that doesn't represent the group, a term that quietly changes meaning.

Which PrepTests to drill from

The industry standard is to drill with PrepTests 139 and lower and save PTs 140 and newer for full timed practice tests. The free diagnostic's drill citations follow that split, and so do I.

Honestly, though, it's mostly a myth. The language of the test has barely changed, and I've never seen any company show real numbers behind it. It's Reddit voodoo. A test built on human language and semantics is hard to verify, and that's how a lot of LSAT myths spread. This is one of them.

There's the smallest bit of legitimacy to it, so I stick by it. But if you don't follow it, it isn't a big deal. Don't let the test get into your head. It's written by very capable psychologists, statisticians and psychometricians, and small details like this aren't what decides your score. If they're getting to you, you might want to pivot careers. (Kidding. Mostly.)

Find your pattern

Your LawHub score report already has what you need to check this. Upload the PDF to the free diagnostic and it sorts your misses by question type, so you can see whether your Strengthen, Weaken and Sufficient Assumption misses cluster together.

For more on the individual types, see Weaken mistakes, Necessary Assumption mistakes and Logical Reasoning miss patterns. If you'd like a second set of eyes on your report, book a free 15-minute call.