#5 - A person can develop or outgrow asthma at any age.

[Administrator]

Complete Question Explanation

Justify-#%. The correct answer choice is (C)

In this stimulus, the author presents several numerical facts about asthma. Before the age of ten, boys are more likely to get asthma, but during early adolescence the girls catch up. By adolescence, the percentage is roughly the same for boys and girls.
The justify question which follows the stimulus is somewhat unique, but perfectly conducive to the prephrase of an answer.

What would allow us to conclude that the number of adolescent boys that have asthma is roughly equal to the number of adolescent girls? Since the percentage is roughly the same, the overall number of adolescent boys and girls would have to be the same for this conclusion to be drawn.

Answer choice (A): This is irrelevant to the comparison of asthmatic adolescent boys versus girls, so this would not justify the conclusion required.

Answer choice (B): Again, the likelihood of these particular children outgrowing asthma is irrelevant to the comparison between the number of asthmatic boys versus girls.

Answer choice (C): This is the correct answer choice and is exactly what was prephrased in the discussion above. Since the percentages are about the same, the totals have to be the same in order for us to conclude that the numbers of adolescent boy and girl asthma sufferers is roughly equivalent.

Answer choice (D): Neither climate nor environment is even alluded to in the stimulus, and this information would do nothing to justify the conclusion of equivalent numbers of asthmatic adolescent boys and girls.

Answer choice (E): Like most of the other wrong answer choices above, this choice is completely irrelevant—adult asthma is not even mentioned by the author, and this information would not justify the needed conclusion, so this answer choice is incorrect.

[rameday]

So i tend to get these questions wrong in LR. I get the idea that in that error type the stimulus wrongly equates a % with a definite quality. so the % could go up without the number of people changing and vice versa.

I think why I get these LR questions wrong is because from a conceptual standpoint I am a tad bit confused as to how that could happen. Math has never been my forte!

Also for an assumption question for example where the flaw is a number and percentage error, is the assumption then that the author assumes that those two things are equal/ equated? For some reason I feel like that is what the author is concluding.

The JTC% question was about asthma between boys and girls and concluded that the % was roughly the same between the two genders. And then to JTC the author had to assume that since the percentage were roughly the same the overall # of adolescent boys and girls would have to be the same.

So I guess I am confused as to how conceptually #'s & % work and why the author would need to assume that they are the same and how it is possible that they could actually be different. I would just like some clarity just to ensure that I am not continuously getting these questions wrong in LR.

A

[KelseyWoods]

Hi A!

The conclusion that we are asked to Justify in this question is actually given to us in the question stem and it is that the number of adolescent boys with asthma is approximately equal to the number of adolescent girls with asthma. From the information in the stimulus, we only know that the percentage of adolescent boys with asthma and the percentage of adolescent girls with asthma is roughly the same. So we need an answer choice that will prove that the NUMBERS are equal when added to the premise that the PERCENTAGES are equal. Answer choice (B) does this by telling us that the TOTALS are the same. So if there are the same total number of adolescent boys and girls, then the same percentage of each group with asthma would equal the same number in each group with asthma.

Numbers and percentage situations on the LSAT often hinge on 3 elements: total, number within the total, and percentage within the total. If you know just the percentage, that doesn't prove anything about the number. If you know just the number, that doesn't tell you anything about the percentage. But if you know 2 out of those 3 elements, then you can deduce the 3rd. So if you know the percentage and the total, you can figure out the number, etc.

In this question, if the TOTALS of the two groups were not equal, then the percentages would not necessarily lead to equal numbers. Let's make up some numbers to apply to the situation to show that the percentage alone is not enough to prove the number:


Adolescent Girls:
Total #: 100
Percentage with asthma: 20%
Number with asthma: 20

Adolescent Boys:
Total #: 200
Percentage with asthma: 20%
Number with asthma: 40

In this example, if there are 200 adolescent boys but only 100 adolescent girls, then the percentage of each group with asthma could be the same (20%) but the number with asthma would be different because 20% of 100 is 20 and 20% of 200 is 40.

Therefore, the only way to prove that the same percentage with asthma = the same number with asthma is to show that the two groups have the same total size.

Hope this helps!

Best,
Kelsey

[akanshalsat]

Hello, in your explanation, where exactly in the stimulus is it saying that we need to prove that the NUMBERS have to be the same? just because the percentages are the same doesn't mean that we need an answer choice that proves that the total number is the same b/c as you said the percentages can be equal even when the numbers of both genders are different.

[Claire Horan]

Hi Akanshalat,

Percentage = # in selected group / # total

The stimulus gives us the premise that the percentage of boys with asthma is equal to the percentage of girls with asthma by adolescence.

So, (# of girls with asthma/ # of girls total) = (# of boys with asthma/ # of boys total)

We are asked to find the answer choice that, paired with the above premise, will lead to the conclusion that # of girls with asthma approximately = # of boys with asthma. Looking at the equation above, if we know that the # of girls total equals the number of boys total, then the number of boys and girls with asthma is approximately equal.

If you're still having trouble understanding, let's put in numbers. Let's say the percentage given in the stimulus is that 10% of girls and 10% of boys have asthma. If we also know, from the correct answer choice, that there are, say, 100 girls and 100 boys, that will mean that there are about 10 girls with asthma and about 10 boys with asthma. We are able to draw the conclusion that the numbers of boys with asthma are equal to the number of girls with asthma.

I hope this helps!