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The 90th percentile [#permalink]
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Official Explanation


The Rth percentile is a value at or below which lie R% of the data values. To find the Rth percentile for a data set, first put the data in order. Next compute k, using the formula \(k = n (\frac{R}{100})\), where n is the number of data values. If k is an integer, the Rth percentile is the average of the kth and

(k + 1)th data values. If k is not an integer, round k up to the next greatest integer, say 1, and then the Rth percentile is the Ith data value. Tip: Do not confuse percentiles with percents .

A percentile is a value that acts as cut point for a specified percent. For the data presented in Quantity A, the value of k for the 90th percentile is \(k = n (\frac{R}{100})= 10 (\frac{90}{100})=9\). Thus, the 90th percentile is halfway between the ninth and tenth values. Hence, Quantity A is \(\frac{100+1400}{2 }= \frac{1500}{2}= 750\). The two quantities are equal.

Tip:In some other publications and online materials, a slightly different definition of percentile from the one given in this answer explanation is given. In those publications/online materials, the Rth percentile is a value below which lie R% of the data values. For continuous distributions (such as the normal curve), the two definitions are equivalent. For the GRE, just think of the Rth percentile as a value that splits the data into two parts so that R% is at or below that value and (100 — R)% is at or above it.
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Re: The 90th percentile [#permalink]
Here n = 9, so it will fall in second case where it should be rounded up to 8.1 ~= 9?
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Re: The 90th percentile [#permalink]
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The above explanation is wrong I guess. It is C the answer not B

Also the question can be solved even with a bit of common sense

The values are

0,0,0,0,100,100,100,100,1400

The middle is 100 of the data set which is also the mean. So the 90th percentile is what is located in the right part of the data set (90 clearly suggests this by the name itself) BUT CANNOT be the upper rightmost value or 1400

So the 90 is exactly the average of the two right-most value: 100+1400/2=750

C is the answer
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