Question: Comparing Apples with Apples

Comment on Comparing Apples with Apples

Hi sir,

When there comes the percentile questions, I only come to know about the basics about percentile and not that much... So, I have found a bit difficulty when tackling percentile based question from 5lb manhattan book. My question is that- Is there any easier way to approach this sort of question?

300 test results are integers ranging from 15 to 75, inclusive. Dominick’s result is clearly in the 80th percentile of those results, not the 79th or the 81st.

Quantity A: Number of other test results in the same percentile as Dominick’s

Quantity B: Maximum number of other test-takers with the same result as Dominick
greenlight-admin's picture

I'm not a huge fan of this question.

The idea is that the word "clearly" means that the other scores in the 80th percentile are all equal.

Since 300 divided by 100 percentiles is 3, the authors conclude that there must be a total of 3 EQUAL data points in the 80th percentile.

This means there must be 2 other scores that are the same as Dominick's score. In other words, Quantities A and B are both equal to 2.

If it is equally distributed.
The range of possible scores is between 15 and 75, aka 60.
So we can see that there are 5 students with the same score for each possible score.
15 - 5
16 - 5
17 - 5

let's check the 80 Percentile.
0.8 * 300 = 240

240 / 5 = 48

Now grades:
15 + 48 = 63
So I see it as 5 students got a score of 63.
How is in your answer and in the answers in the original post with this question, everyone assumes that there are 3 students with the same score (I understand the concept of the bin with 3 when dividing 300 by 100, but here I think it is not very useful).

Also, it assumes that everything is equally distributed.
It is possible that the score is 15,15,15...15,15,75, then we have 299 students with the same score, but I think it is a different question.
greenlight-admin's picture

I reread the question, and I'm still hung up on what "clearly" is intended to mean.
I should note that there are actually 61 possible scores from 15 to 75 inclusive. So, we can't divide all 300 scores into 61 possibilities.
I'm going to delete this post shortly.
I don't think it is adds any value to anyone's GRE prep.

I am having problem in approaching percentile questions?
How can I gain more insight.

Hi Brent, not quite sure why is 13.5% & 2.5% here as compared to in the lessons you mentioned that in a normal distribution is 34% 14% 2% and so on...? Could you help clarify? Thanks Brent
greenlight-admin's picture

The test-makers are rounding the actual values to the nearest unit.
That said, the GRE won't give you a question that hinges on 13.5% vs 14%.

Thanks Brent. So we can stick to 34% 14% 2% in normal distribution question for calculation on test day then?
greenlight-admin's picture

Yes, those numbers will work.

Thanks Brent for confirmation.

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