OpenEuphoria

Re: Mathematicians !! Percentile/Quartile function

• Posted by Pete Stoner <stoner.pete at gmail.com> Sep 07, 2005
• 616 views

Pete Stoner wrote:
> 
> Pete Stoner wrote:
> > 
> > Pete Lomax wrote:
> > > 
> > > On Wed, 07 Sep 2005 09:45:41 -0700, Pete Stoner
> > > <guest at RapidEuphoria.com> wrote:
> > > 
> > > >i.e. for values of {2, 6, 7, 10, 14, 15, 16} the quartiles are 6.5, 10
> > > >and 14.5
> > > >but for a range of {2, 6, 7, 10, 14, 15} the correct quartiles seem to be
> > > >6.25, 8.5 & 13
> > > FWIW, (and strictly from observation only!) the first is (or might be)
> > >  (6+7)/2, 10, (14+15)/2, while ths second is (or might be)
> > > (2+6+7+10)/2, (7+10)/2, (10+14+15)/2
> > > 
> > > As I don't have either Excel or 123 to hand, I can't experiment more,
> > > but I wonder what happens with sets of longer numbers.
<snip>

I found this interesting article
http://www.gslis.utexas.edu/~wyllys/IRLISMaterials/quartiles.pdf
which explains how Excel (and I presume 123 'copied' them  ) calculates its
quartiles and suggests it is 'wrong' or "the algorithm clearly
yields results, even in certain simple cases, that fail to accord with what most
people who use quartiles expect to see.".... "This [makes] the algorithm . . .
neater from an IT syntax perspective, but less accurate mathematically.".
For the small example they give (even qty of values)  Juergen and I get the
  same results as they do, whereas Excel gives different numbers

so I think I'll stick with what I've got..

Thanks all
Regards Pete.