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I am confused on the method to find the 1st and 3rd quartiles.

Suppose given a data set 2,5,6,9,10,11,13,17 with an even number of data. What is the formula to find the first and 3rd quartiles?

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Have you tried googling for the formula? – cheepychappy Oct 4 '12 at 11:20
There are different ways to compute quartiles. Try this – Patrick Li Oct 4 '12 at 11:31
up vote 1 down vote accepted

The basic problem in finding quartiles is simple: It has no specific (I mean mathematically exact) meaning. Similar can be said about percentiles, etc., also. What value you get depends on what convention you are using. Conventions differ from person to person. Some of the conventions being used can be found in the MathWorld page for Quartile.

So, for your case, my advice would be to check the book you are using and use the convention followed there. However please keep in mind that these are not cast in stone.

But it must be noted that these differences in conventions only matter if your sample size is small. If your sample size is large, then these distinctions don't matter.

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