PT26.S3.Q24 - over the last 25 years, the average price paid

ENTJ

http://7sage.com/lsat_explanations/lsat-26-section-3-question-24/
This question is beyond sucky. Did anyone else have any problems with determining the right answer for this question? Thanks.

vandyzach

Sometimes on questions like these where the argument is super-complex, instead of trying to tell myself the flaw in my head, I just go into the questions with the ARGUMENT, rather than the FLAW, in mind.

So on this weaken question, we know this is not a valid argument. But looking at the argument, it seems like a pretty strong one, at least compared to most other LSAT arguments.

So I went into the answer choices thinking to myself, "Which of these answer choices makes it less likely that, because over the last 25 years, the ratio of price paid per car to individual income has increased, that individuals who buy new cars spend a higher proportion of their income on those cars?".

When I got to (E), I thought, "Oh, well this means that lots of big new cars were bought by businesses and the government, so this could be a reason that the average price paid per car relative to individual income has gone up, yet individuals do not spend a higher portion of their income on cars".

The other answers don't even come close to giving us that.

Since I couldn't really tell myself what the flaw exactly was, I just instead understood the argument and went into the answer choices with an open mind (which is really important for weaken questions in my opinion).

Another key that helped me get through this one with no problem was realizing that this was a pretty dang good argument! So a weakener could come out of left field- and it did: entities other than individuals are the ones buying the new cars!!!!

Hope that helps!

CFC152436

Edit: Looks like Zach beat me to the punch. Feel free to ignore my explanation haha. The flaw is subtle, and it's a different flaw than most proportion questions, but it's definitely there.

Just took a look - definitely one of the harder LR questions. To get this right, you either need to catch the assumption while you're reading the stimulus, or be really adept at eliminating wrong answer choices that are out of scope.

Premise:
The average price paid for a new car has increased in relation (proportionally) to the average individual income over the past 25 years. This premise is simply a ratio, and we can represent it as a fraction: "avg. price paid for a new car / avg. individual income." When you divided this fraction in 1970, the decimal was 0.05 (avg. price for a new car was $1, and the avg. income was $20). According to the premise, the ratio has gotten bigger over the past 25 years - this means when you divided the fraction in 1995, you got 0.4 (avg. price for new car was $20, and the avg. income was $50). Nothing overly complicated here, just a simple proportion.

Conclusion: Individuals who buy new cars spend, on average, a larger proportion of their incomes than did individuals 25 years ago. Great, another proportion. This one can be represented as the following: avg. price paid for a new car by individuals / avg. individual income.

Write out these two ratios on a piece of paper (or see them in your head), and it's pretty obvious where the author goes wrong. The top half of the ratio in the premise isn't the same as the top half of the ratio in the conclusion. He's assuming that average price paid for a new car in 1970 is the same as the average price paid for a new car by individuals in 1995. This is by no means a valid assumption. It is certainly possible the premise (the average price paid for a new car) is based on data from companies, business, families, governments, etc who were buying cars. With this in mind, we have no logical right to draw a conclusion about individuals who buy cars.

A. Out of scope. Who cares about households? Our argument certainly doesn't.
B. Out of scope. Who cares about used cars? Our argument certainly doesn't (is there in echo in here?)
C. Strengthens the argument. Shows that the bottom of the proportion is getting smaller, which would provide evidence that the ratio is getting bigger.
(D) Out of scope. Not interested in the entire population, I'm interested in a specific part of the population (i.e. individuals who are buying cars)
(E) Bingo! If individuals now make up a smaller proportion of new-car sales than they did 25 years ago, then the notion of "average price paid" is no longer comparable between individuals from the two different time periods.