Sample LSAT Question – Logical Reasoning (Assumption)

Question

Stimulus:

New parents often install baby monitors so they can hear when their baby cries during the night. However, researchers found that the constant low-level static from baby monitors may actually interfere with parents’ sleep, reducing overall sleep quality. Therefore, baby monitors are counterproductive and should not be used.

Question:

Which of the following is an assumption required by the argument?

A) Some baby monitors can filter out static noise completely.

B) Parents are unable to sleep through low-level background noise.

C) Parents would sleep better if they did not use baby monitors.

D) Crying is the only way a baby can communicate distress at night.

E) All baby monitors produce the same level of static.

Answer 1

I'm Andrew and let's figure this one out with a easy, practical methodology! Are you ready?

1. With any logical reasoning question, the first step is to look at the question type. This will give us a clue on how we should be approaching the passage, especially when time is scarce.
2. In this case, the question type is what's known as an assumption need. What that means for us right now is that when we read the passage, we are on the lookout for a jump in reasoning between evidence and conclusion, otherwise known as an assumption. So lets take a look!
3. The evidence is that baby monitors can interfere with parents' sleep. The conclusion is that baby monitors are counterproductive. See the jump? We need to find a way to bridge these two ideas.
4. Now, I'm not going to pretend like I've figured out this answer before I looked at the choices! On a subjective multiple choice exam, especially a tricky one like the LSAT, our job is to fit their answers into our framework that we've developed from a careful reading of passage and question type.
5. So let's take a closer look at the question type: its an assumption need. That means that the argument needs the "bridge" if it were to be true. To put it a different way, if there was no "bridge", the argument would fall apart.

That's how one breaks down a question on the LSAT! No tricks, complicated formulas, or guessing - just reading and recognizing. The hard work is over and I haven't even looked at the answers yet! That part I'm leaving up to you - tell me what you think :)

Answer 2

Correct Answer: C

How I would walk a student through this:

I’d start by identifying the conclusion: Baby monitors are counterproductive and should not be used.

Then we look at the premise: baby monitors cause static, which disrupts sleep.

So what must be true for the conclusion to logically follow? That without baby monitors, parents would sleep better — otherwise, we can't say they’re counterproductive.

Let’s test the answers:

1. A: Even if some filters exist, the argument assumes monitors in general cause sleep problems. This is not required.
2. B: The argument doesn’t require all parents to be light sleepers — just that static affects sleep. Too specific.
3. C: Yes — if parents wouldn’t sleep better without the monitors, the conclusion falls apart. This is a required assumption.
4. D: Irrelevant to the argument about sleep quality. Eliminate.
5. E: Again, too strong — the argument doesn’t hinge on all monitors being the same.

Conclusion:

This is a classic necessary assumption question. I help students identify these by teaching the Negation Test — if negating the answer destroys the argument, it’s necessary. That’s exactly what happens with choice C here.