Definition talk:Quartile

I'm not sure about the statement: "Let $D$ be divided into precisely $3$ classes."

Is it not 4 classes?
 * 1: Smallest to 1st quartile
 * 2: 1st quartile to median (2nd quartile)
 * 3: 2nd quartile to 3rd quartile
 * 4: 3rd quartile to top.

By the name "quartile" you mean the boundary between the 4 classes in question, I gather - now maybe I misunderstood this when I did this subject some time back (never got to grips with it, the subject didn't interest me much), but I thought the quartiles were the actual divisions (i.e. classes) themselves: 1st, 2nd, 3rd and Top Quartiles. I may well be wrong. There is confusion here in the minds of students which needs to be cleared up. --prime mover (talk) 21:23, 14 October 2012 (UTC)


 * I've checked on wikipedia and the quartiles are indeed the points, not the classes they divide the range into. --prime mover (talk) 21:25, 14 October 2012 (UTC)


 * I have to think about how to present this most clearly. The current state of the page is wrong, but I have to work out what the best way is to present the definition. There are three quartiles, which are numbers. The quartiles divide the data into four sections. --GFauxPas (talk) 21:33, 14 October 2012 (UTC)


 * It's actually done quite well in Wikipedia. Is your book not very good? --prime mover (talk) 21:35, 14 October 2012 (UTC)


 * The book is fine; I'm not very good today. --GFauxPas (talk) 21:38, 14 October 2012 (UTC)

Quartile or Quantile?
Reading through this definition, I'm not sure whether you're confusing the concepts of "quartile" and "quantile". --prime mover (talk) 21:27, 14 October 2012 (UTC)
 * I'm specifically trying to define quartile. Still working on your above comment, though. --GFauxPas (talk) 21:30, 14 October 2012 (UTC)


 * And I'm still trying to make sense of $\dfrac Q n$ and $1 - \dfrac Q n$ because it does not seem to make sense.


 * If you have 100 data points, then for $Q = 1, 2, 3...$, $\dfrac Q n = \dfrac 1 {100}, \dfrac 2 {100}, \dfrac 3 {100}$ etc. which does not make any sense. --prime mover (talk) 21:33, 14 October 2012 (UTC)