Percentile Question

GRE Quant Problem Solving
1

Hi all, I hope you are all having a lovely day. I encountered the following question and, as some of you may know, the answer is A, as the 15th percentile is to the left of the line designated as -1 (less than one standard deviation).

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However, I am struggling to reconcile this with a quant concept that I have written down which is that: the 20th percentile are numbers greater than the first 20% of the data, in my head this makes it so that the 20th percentile would be (effectively) that first value at 21% of the data, which starts pushing it, in the case of the above question, awfully close to the 16th percentile, and therefore the single standard deviation line. I feel like, regardless, you get the same answer. But I thought I would enquire.

I look forward to hearing everyone’s input!

2

Not sure if you had a typo but a “score” in the 20th percentile, for example, could mean either:

  1. 20% of the “scores” are equal to or below it

  2. 20% of the “scores” are below it

I think the GRE uses the definition in 2)

As for the actual question u posted, the 15th percentile is just a “little bit” over 1 standard deviation from the mean (as depicted in the figure).

So if 470 - 340 = 130 goes beyond 1 standard deviation then the standard deviation must be less than 130.