LSAT 154 | Section 2 | Logical Reasoning: Q19

LR Question 19 Explanation

QUESTION TEXT: Doctor: The patient had been experiencing back and leg pain…

QUESTION TYPE: Necessary Assumption

CONCLUSION: Pressure on the nerve caused inflammation, which caused the patient’s back and leg pain.

REASONING: Cortisone injection can treat nerve inflammation. The doctor treated the patient with a cortisone injection and this resulted in pain relief.

ANALYSIS: This doctor decided the patient’s pain could only be due to one thing, and confirmed their conclusion when their prescribed treatment worked. This doctor is committing a correlation doesn’t equal causation flaw. To ensure that the argument isn’t flawed, we need an assumption that rules out another factor that could’ve resulted in the pain relief.

___________

1. This is both extreme and irrelevant (“most accurate”). We don’t care about this.
2. This would disprove the doctor’s conclusion.If the cortisol injection didn’t reduce pressure on the inflamed nerve, then pressure on the inflamed nerve wasn’t the cause of the patient’s pain.
3. CORRECT. This rules out the alternate possibility that the reduction in pain was due to the placebo effect. If we negate this (“the reduction in pain was due to patients’ belief in cortisone”) then it weakens our conclusion that that the pain was due to pressure on the nerve.
4. The doctor says that cortisone is the best way to treat this, not the only way.
5. We’re only concerned about this one patient, not what “usually” is the “best” (extreme) treatment.

Recap: The question begins with “Doctor: The patient had been experiencing back and leg pain”. It is a Necessary Assumption question. Learn how to master LSAT Necessary questions on the LSAT Logical Reasoning question types page.