Q22 - Over the last 10 years

[yusangmin]

Sorry for the bombardment

this one really stumped the crap outta me

i cant even begin to fathom how under 18s indicates that older

is this because if there are people extremely young pulling the weight down,

theres gotta be another force from the older tier of the population pulling the average
age up?

how the #$#%# would u even come to this conclusion during test day when u have
1-2 minutes for a question.wow.

even so, isnt it equally possible that there are just as many 60 year olds or 57 year olds who aree pulling the average age up, not 65 yr olds and older?

thanks!

[ManhattanPrepLSAT1]

This one has boggled people ever since it appeared on that test. I think the most difficult part is how counter intuitive it is and how it plays off another logical reasoning question type. If we were trying to explain why average age increased, an answer choice like (B) would be very tempting. Answer choice (B) states that the birth rate has decreased over the past 10 years. If there are less babies around, people usually say to themselves, "that's why the average age increased! This has got to be the answer."

However, our goal is not to explain a result, but rather strengthen the conclusion. We know the average age increased from 52 to 57. There are two obvious explanations for why the average age would increase. First, that the number of older people (over 65) has increased. Or second, that the number of younger people decreased. The argument concludes that it's the first of these two options. However, the argument failed to consider that it was the latter option. To support the conclusion, let's reinforce the notion that its the first option by challenging the possibility that it's the second option.

Another way to see this would be

If there were only two ways to get to school, ride the bus or walk. If I want to support the idea that you walked to school today I could undermine the idea that you took the bus. Just by saying that you did not take the bus, I have supported the idea that you walked to school.

So, in this example. To support the idea that we have more old people, I want to say that it is not the case that we have less young people. By saying that we have more young people, I make it all the more likely that there are more old people. Otherwise, why did the average age go up? Answer choice (A) says that it's not for a decrease in young people that the average age went up. Answer choice (A) eliminates an alternative explanation.

(A) is correct for the reasons above.
(B) weakens the argument by supporting an alternative explanation for why the average age went up.
(C) doesn't tell us about the average age of those people. Who cares that there are more of them, I need to know how old they are!
(D) is irrelevant. Same problem as answer choice (C).
(E) is irrelevant. The argument is not a comparison between this region and surrounding regions, but rather a comparison of this region at one point in time with the same region at another point in time.

[brandblum]

How does answer A) strengthen the argument? Why wouldn't B)?
Thanks.

[bbirdwell]

So here's the argument in a nutshell:

The average age increased from 52 to 57.

Therefore, there has been a dramatic increase in the number of people over the age of 65.

Is that logical? Aren't there other things that could be responsible for the change in average age?

(A) states that the number of really young people has increased. This would make it hard to increase the average age so much. With this in mind, the conclusion now makes more sense -- it now seems more feasible that more really old people moved to the area, compensating for the big increase in average age.

(B) does exactly the opposite. It states that there are fewer infants around to weight down the average age. That alone could be enough to cause the increase in average age. This is a classic weaken answer choice because it offers an additional potential cause for the result cited (increase in average age).

Seeing it clearly as a causal argument really helps. Know what I mean?

[ohsobecca]

Okay, I get your reasoning on this question but how did you know that "a dramatic increase in the number" meant that old people had MOVED to the region? That is not clear to me from the stimulus at all. I picked (B) initially b/c I didn't interpret the stimulus as asking us to bolster the idea that old people had moved in; my reasoning was that the number of old people living in the region increased relative to the population. That's why I chose B. If there are significantly fewer births while the old people are just getting older, the number of old people is increasing. No?

[bbirdwell]

I didn't interpret the stimulus as asking us to bolster the idea that old people had moved in

We are to bolster the idea that there are more people over the age of 65. They don't necessarily have to have moved in.

If there are significantly fewer births while the old people are just getting older, the number of old people is increasing

No, the number of old people is not increasing. The proportion of old people to young people would increase, and thus the average age would rise. This would explain the rise of the average age from 52-57. And that's not what we want. We want the a "dramatic increase in people over the age of 65" to explain that rise.

(A) does this. If the number of youngsters increases, we'd expect the average age to decrease. The only thing that would explain that would be a corresponding (and greater) increase in the number of old folks.

[alinanny]

B is wrong because you are not trying to explain why the average age of the population went from 52 to 57 but instead strenghten the conclusion that more people over the age of 65 are living in the region. If the birth rate decreased significantly in the last ten years then the population is getting older in average but that doesn't mean that there are more older people only that there are less younger people so the average age goes up.
A on the other hand implies that even with an increase in the younger population the average age still went up so there has to be more older people to account for this increase in the average.
I know this has probably been said above but hopefully I can help someone out!

[shaynfernandez]

Is this a justify the conclusion question?

[jamiejames]

Is this a justify the conclusion question?

Excellent question. I can see how you might think this, but we're not trying to justify the conclusion, we're trying to strengthen it.

Justifying requires you to find an answer that logically proves the conclusion. It lends such strength that the conclusion must follow. We're not asked to prove the conclusion here.Strengthening means giving an answer that best supports the conclusion, it doesn't necessarily have to prove the conclusion.

A is correct in this case, because it eliminates the possibility that there are fewer younger people in the area, thus strengthening the conclusion that more people over 65 moving into the area has resulted in an increased average age.

[jamiejames]

I just thought I'd add something here, this is probably one of the most important questions on a past LSAT to study. It shows that strengthening an argument doesn't have to come in the form of adding something to the argument to reinforce the conclusion, but also you can show that a possible other cause that could weaken the conclusion is not the case, thus strengthening it.

[xingdavid]

Does anyone know of a question that uses similar techniques to this one?

[sumukh09]

Whooooooooooaaaaaa Is my reaction to this question.
Definitely one of the more tricky ones that require you think outside the box. At first glance, you would never think that A) would be a viable candidate to be the correct answer. But I guess after the explanations given above it makes a lot of sense; A) strengthens the idea that REALLY old people must moved into the region because if the number of young people increased then there would have to be something that offsets that influx of youngn's given the increase in average age. Thought I'd give my 2 cents - this is actually a really good Q but hopefully this is the last one....ever.

[Dannyboy3D]

Everything I've read so far can get really misleading, and it's not too hard answering this question as long as our thinking caps are on...

How do we strengthen the idea that there are more 65-year-olds living in the region, knowing that the average age went up from 52 to 57?

A) says in the last 10 years, there was an increase in the number of people 18-and-under.

If that were true, simple math would tell us that this phenomenon would have BROUGHT DOWN the "52 to 57" average age increase. But then, how in the heck did that average age go up anyway?

Something must have offset the increase in people 18-and-under...something like the conclusion in the stimulus: there had to have been a dramatic increase in older people.

In other words, even though the number of younger people increased, the average age still went up from 52 to 57 because there had to have been an increase in older people too. With A), we can validate the conclusion.

[christine.defenbaugh]

Everything I've read so far can get really misleading, and it's not too hard answering this question as long as our thinking caps are on...

How do we strengthen the idea that there are more 65-year-olds living in the region, knowing that the average age went up from 52 to 57?

A) says in the last 10 years, there was an increase in the number of people 18-and-under.

If that were true, simple math would tell us that this phenomenon would have BROUGHT DOWN the "52 to 57" average age increase. But then, how in the heck did that average age go up anyway?

Something must have offset the increase in people 18-and-under...something like the conclusion in the stimulus: there had to have been a dramatic increase in older people.

In other words, even though the number of younger people increased, the average age still went up from 52 to 57 because there had to have been an increase in older people too. With A), we can validate the conclusion.

Thanks for your contribution Dannyboy3D! Your reasoning here is mostly on target!

I do have one rather significant correction though: there did not have to be a dramatic increase in older people. Answer choice (A) does not validate, or prove, the conclusion, it simply strengthens it.

In order to reconcile the premise with (A), we would need something to offset those young'uns, but that could have come in any number of formats: maybe all the the 18-52 year olds left the region. Maybe there was a massive increase in the population age 57-65. Or maybe the 65+ crowd increased. Any of those could solve it.

But fortunately, strengtheners do not need to validate/prove the conclusion, they only have to move the ball a little bit down the court.

For this reason I often caution students to begin by identifying the gap between the premise and the conclusion, and then hunt for a choice that helps bridge that gap. Starting by combining each answer choice with the premise, and then looking for what conclusion would have to follow can easily lead you astray.

(A) strengthens by removing a potential alternate explanation for the average age increase, thereby making it a tiny bit more likely that an increase in the 65+ crowd is the real culprit.

Please let me know if you have any questions!

[rioben]

Are there any similar questions to this (for practice)?

[hyojin.j]

Thanks for awesome postings above.

My logic was essentially the same as what some of you guys wrote above, but instead of going lengthy, I just wrote the simple math formula:

*Average age = sum (age of ppl)/ no. of ppl

Pre: * increased from 52 to 57
Con: increase in no. of ppl whose age is over 65

when ppl under 18 increase * will decrease accordingly. But the evidence says the * has gone up. then what other explanation do we have? Like the conclusion states there is an increase in the no. of old ppl.

That formula just helped me understand what was going on in the sti and walk through answer choices more easily without getting lost in my thought.

[salach]

I've never posted here before but I think the best way to think about this is relatively simple.

The argument is stating that there has been a dramatic increase in the number of people over age 65, with the evidence that the average age has increased from 52 to 57.

The first thought that popped into my mind was "well couldn't a lot of 60-year olds have just moved to the region?" That would probably be sufficient to increase the average age and wouldn't require the conclusion.

The only answer that actually addresses that issue is A) by suggesting that it wouldn't be possible for just a lot of 60-year olds to have moved to the region to move the average age from 52 to 57 if SIMULTANEOUSLY there were also a lot more 18 year olds in the region dragging the average age down.

Hope that is remotely helpful but it helped me.

[DPCTE4325]

So here's the argument in a nutshell:

The average age increased from 52 to 57.

Therefore, there has been a dramatic increase in the number of people over the age of 65.

Is that logical? Aren't there other things that could be responsible for the change in average age?

(A) states that the number of really young people has increased. This would make it hard to increase the average age so much. With this in mind, the conclusion now makes more sense -- it now seems more feasible that more really old people moved to the area, compensating for the big increase in average age.

(B) does exactly the opposite. It states that there are fewer infants around to weight down the average age. That alone could be enough to cause the increase in average age. This is a classic weaken answer choice because it offers an additional potential cause for the result cited (increase in average age).

Seeing it clearly as a causal argument really helps. Know what I mean?

This question was really tough for me at first because I didn't immediately identify the causality in the argument.

Curious Fact: Why did the average age increase from 52 to 57 over the past 10 years?

Author's Story: Dramatic increase in 65+ year olds over the past 10 years.

Causal Strengthen Tasks:
1) Get rid of an alternate explanation
2) Increase Author's Plausibility via No Cause/No Effect

What are some alternate explanations? Well, this has to do with averages. One way for an average to go up is by more old people. Alternatively, said average can also go up by fewer young people.

Answer choice (A) gets rid of an alternate explanation by saying "Hey! It's NOT the case that the average age increase occurred due to there being FEWER young people."

Answer choice (B) is tricky but if you read carefully it's not that tricky. B says the birth rate DECREASED. Consider the implications of the opposite being true (the correct opposite answer should theoretically weaken if it indeed is an alternate explanation): birth rate over the last 10 years has increased Doesn't this strengthen? The birth rate increased, which means MORE younger people, which means it's that much more likely that it was, in fact, more 65+ year olds.

Answer choice (D) I initially found D really attractive but in order for D to be correct, you really need add in a lot of your own assumptions. Mainly, you would need to assume that MORE young people moved into the region than moved out. This would lead to there being a net INCREASE in young people, which does the same thing that answer choice A does by ruling out the opposite (if there was a net DECREASE in young people, that'd be an alternate explanation).

Thoughts?

[ohthatpatrick]

Sounds good.

I would caution you against thinking of your Causal Strengthen tasks in the way you wrote it:

Causal Strengthen Tasks:
1) Get rid of an alternate explanation
2) Increase Author's Plausibility via No Cause/No Effect

The No Cause/No Effect is just one variety of increasing plausibility. There's no reason to limit #2 to increasing plausibility via that one possible mechanism (that happens to be the most common mechanism, but you'd be limiting your thought process to think of #2 that way)

It would be like writing #1 as
1) Get rid of the reverse causality alternate explanation

That's one possible alternate explanation, but we'd be strengthening by decreasing the plausibility of ANY type of alternate explanation.

I'd probably say think of your Causal Strengthen Tasks as:
1) Lower the plausibility of some OTHER CAUSAL STORY
2) Increase the plausibility of the AUTHOR'S CAUSAL STORY

For (B), I don't think you need to jump through as many hoops. (B) weakens.
It provides the very alternate explanation that (A) undermines.

When we thought, "How ELSE could you explain a shift in average age from 52 to 57 yrs old?", we thought: more older people or fewer younger people.

The author chooses "more older people".

(A) undermines the plausibility of "fewer younger people"
(B) increases the plausibility of "fewer younger people"

And, yes, for (D) there's no way to work with it because it doesn't contain any information about age demographics.