LSAT 131 | Section 3 | Logical Reasoning: Q12

LR Question 12 Explanation

QUESTION TEXT: To cut costs, a high school modified its air-conditioning

QUESTION TYPE: Necessary Assumption

CONCLUSION: Lowering humidity can make people sick.

REASONING: A change in the air conditioning lowered humidity by 18%. Then there was a 25% increase in visits to the school nurse.

ANALYSIS: An increase in sickness can be due to many causes. The fact that the visits happened at the same time as the decreased humidity doesn’t prove the humidity caused the sickness.

Basically, this argument only showed us a correlation, and assumed there was causation. You can’t do that. The necessary assumption is that the two events were actually linked.

The right answer takes an interesting turn and points out that the nurse’s visits might not even have been due to illness. Who knows, maybe people just wanted out of class that day for some reason.

___________

1. CORRECT. If this isn’t true, then the argument is baseless.
   Negation: None of the school visits to the nurse were due to illness.
2. We don’t need most students to suffer. We only need enough people to suffer that there will be a 25% increase in nurse’s visits.
   Negation: Only half of students suffered from the decrease in humidity.
3. Why on earth would this matter? People might have felt ill, say, 22 hours later, still gone to school, and visited the nurse once they felt sick. (Which would have been at, say, 10 am instead of noon.)
4. We don’t care if there’s an exact 25% probability increase. The increase referred to nurse’s visits, not illness. (It’s possible that not everyone who got sick went to the nurse. Also, the baseline rate of nurse’s visits might not all be due to illness.)
5. Cost effectiveness isn’t relevant to the argument. The conclusion was only about whether decreased humidity can cause sickness.