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

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.