PT 12. Section 1. Question 19

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stl

Posts: 9
Joined: Sun Oct 05, 2008 1:34 am

PT 12. Section 1. Question 19

Could someone please explain to me why the correct answer is correct? Thanks!

The use of automobile safety seats by children aged 4 and under has nearly doubled in the past 8 years. It is clear that this increase has prevented child fatalities that otherwise would have occurred, because although the number of children aged 4 and under who were killed while riding in cars involved in accidents rose 10 percents over the past 8 years, the total number of serious automobile accidents rose by 20% during that period.

Which one of the following, if true, most strengthens the argument?

Correct answer: The proportion of serious automobile accidents involving child passengers remained constant over the past 8 years.

Atlas LSAT Brian

Posts: 31
Joined: Thu Jan 28, 2010 6:12 pm

Re: PT 12. Section 1. Question 19

Hi. I'll give it a try.

Two things I noticed first about this argument: it's a causal argument (the increase in car seats is preventing fatalities), and the evidence is percentage-based (serious accidents went up 20%, while child fatalities rose just 10%).

Before looking at the choices, I tried to identify possible logical gaps or assumptions in the argument. One big question that came to mind was "How many accidents include children?" Again, the point the author is making is that, since accidents increased by 20% but child fatalities increased by only 10%, the car seats are preventing fatalities, because presumably, a 20% increase in accidents should yield a 20% increase in child fatalities. But in order for that to be logical, it must be true that all the new accidents (the 20% increase) included the same amount of accidents involving children as accidents usually do.

In other words, if none of the accidents in that 20% increase involved children, then the car seat isn't necessarily helping -- rather, there just aren't as many kid in accidents. So if the car seat is indeed responsible, we must assume that there are still just as many kids involved in accidents as there used to be.

Answer choice (B) essentially validates this assumption. It says "The proportion of kids/accidents has not changed." This means that the 10% increase in child deaths is indeed less than the corresponding 20% we might have expected, thus strengthening the idea that the car seats are preventing deaths.

(A) kids over 5? Who cares. The argument is about those under 4.
(C) kids are taking more, shorter trips? It's unclear how this affects the argument, which relies on accidents and deaths. Number of trips is unrelated.
(D) out of scope. The argument doesn't break the "under 4" category into smaller categories.
(E) number of adult fatalities is out of scope and unrelated.

Hope that helps!

willwash

Posts: 308
Joined: Mon Jan 25, 2010 9:51 pm

Re: PT 12. Section 1. Question 19

So if there were 1000 serious accidents per year (for example) 8 years ago, and exactly half (for example) involved children, that's 500 serious accidents involving children per year. If there's been a 20% increase overall, to 1200 serious accidents per year, and IF the ratio of serious accidents invovling children is still exactly half, then that number increases to 600 serious accidents involving children per year.

What you have, basically, is an increase in the total number of serious accidents involving children of 100, yet in the same time, there are only 50 more child fatalities, 50 less than would be expected. Some other factor is contributing to that deficit, and the argument says it's the safety seats.

pattymac

Posts: 210
Joined: Wed Nov 04, 2009 7:44 pm

Re: PT 12. Section 1. Question 19

What also helped me was how brutal the other answers were. I did this 3 nights ago and I wasn't 100% on the answer as much as I was 100% on the others being dead wrong. Think of things in the simplest terms possible when you're dealing with percentages. You don't have to think in the 1000's, 10 would do since theres no hard numbers given. This helps me anyways.

I think if you're confused on a percentage/numbers question and theres an answer where it talks about a previosu decade or time passing w/ a strengthen/weaken question, check the first answer that says something about being the same. Always seems a good starting point for me. Make sure it's within the scope though! So if you got the argument, say:

Last year, more than half the cities stop signs were vandalized but after increased police supervision, only one quarter of the of the stop signs were vandalized. Thus, an increase in police supervision led to an improvement in the condition of stop signs.

An assumption answer might look like "there was not an increase in the number of stop signs produced last year". (because if there was, the police supervision wasn't the result of the decrease in vandalism; the number of signs went up while the vandalism remained constant or may have even gone up, so the conclusion does not follow. If there were 4 signs last year and it doubled to 8, then in the previous year 2 were vandalized while the next year 2 were vandalized. Same if the number of signs quadrupled to 16, last year 2 were vandalized where the next year 4 were vandalized. Thus the police inteverention did nothing to deter.)

A strengthen answer might look the same: "the number of street signs remained the same in the two year period" (thus, if there was 4 signs the year before and 1 was vandalized and the signs remained the same at 4 but this year there was only 1 vandalized, the conclusion does follow).

A weaken answer might be the opposite in that "there was an increase in the number of stop signs in the two year period" (see the assumption answer).

and of course...

a shell game answer might say "there was an increase in the number of total signs last year"...which would be wrong because we're talking about STOP signs!!!

Hope that helps!

stl

Posts: 9
Joined: Sun Oct 05, 2008 1:34 am

Re: PT 12. Section 1. Question 19

Thanks for all the help everyone. Question makes perfect sense now.