LSAT 104 | Section 1 | Logical Reasoning: Q23

LR Question 23 Explanation

QUESTION TEXT: Research indicates that 90 percent of extreme…

QUESTION TYPE: Flawed Reasoning

CONCLUSION: Tom must be an insomniac.

REASONING: Almost all insomniacs drink a lot of coffee. Tom drinks a lot of coffee.

ANALYSIS: This mixed up correlation and causation.

If you’re an insomniac, sure, you’re likely to drink coffee.

But we don’t know that coffee drinkers are insomniacs. That’s backwards.

Maybe 90% of the entire population drinks coffee, both insomniacs and restful sleepers.

___________

1. This misstates the evidence. We don’t know how many coffee drinkers are insomniacs.
2. The argument never said coffee was the only cause of insomnia. You might get insomnia without coffee, and you might sleep well even if you drink coffee.
3. CORRECT. We have no idea how well coffee drinkers sleep. We only know that people who can’t sleep well drink coffee. But maybe everyone drinks coffee.
4. There’s no problem with this, it can be perfectly find logic. For example: “All dogs have tails. Therefore Fido the dog has a tail.”
5. The conclusion just says it’s “likely” that Tom can’t sleep. The argument didn’t say coffee always causes insomnia.

Recap: The question begins with “Research indicates that 90 percent of extreme”. It is a Flawed Reasoning question. Learn how to master LSAT Flaw questions on the LSAT Logical Reasoning question types page.