Incidentally, MS Excel uses the same quantile algorithm as S+ - and Bill
Gates is never wrong.
Dr. M.Sawada
Assistant Professor, GIS
University of Ottawa
Dept. Geography
P.O. Box 450 Stn. A
Ottawa, ON K1N 6N9
Tel: 613-562-5800 x1040
Fax: 613-562-5145
Eml: msawada@uottawa.ca
-----Original Message-----
From: s-news-owner@lists.biostat.wustl.edu
[mailto:s-news-owner@lists.biostat.wustl.edu] On Behalf Of Prof Brian
Ripley
Sent: Friday, December 07, 2001 11:32 AM
To: Heeringa W.J.
Cc: s-news@lists.biostat.wustl.edu
Subject: Re: [S] Quartiles
On Fri, 7 Dec 2001, Heeringa W.J. wrote:
> Dear S-PLUS users,
>
> Assume I have the following range:
> 1 2 3 4 5 6
>
> Next I calculated the 1st Quartile, the median and the 3rd Quartile in
> both, S-PLUS and SPSS:
>
> 1st Quartile : S-PLUS: 2.25 and SPSS: 1.75
> median : S-PLUS: 3.5 and SPSS: 3.5
> 3rd Quartile: S-PLUS: 4.75 and SPSS: 5.25
>
> Or for this range:
> 1 2 3 4 5 6 7 8
>
> the results are:
>
> 1st Quartile : S-PLUS: 2.75 and SPSS: 2.25
> median : S-PLUS: 4.5 and SPSS: 4.5
> 3rd Quartile: S-PLUS: 6.25 and SPSS: 6.75
>
> So S-PLUS and SPSS give different results. Which results are correct?
> And how can these results be explained?
Why don't you send a bug report to SPSS if they don't explain their
results? If it's not in the on-line help it is a bug, but for S-PLUS it
*is* there.
There are several slightly different definitions of quantiles (and hence
quartiles), but ?quantile in S-PLUS tells you what it uses.
--
Brian D. Ripley, ripley@stats.ox.ac.uk
Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/
University of Oxford, Tel: +44 1865 272861 (self)
1 South Parks Road, +44 1865 272860 (secr)
Oxford OX1 3TG, UK Fax: +44 1865 272595
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