[Openspace] quantile plot

[Julia Koschinsky]

Michael,

One of the reasons why you can end up with different numbers of observations
in your quintile categories is if you are using count data that is skewed,
for instance has a lot of zeros or small numbers (as is the case with
certain mortality or risk data). In those cases, the computation of break
points is unreliable because there are ties between the frequently occurring
values. The use of rates instead of counts is more appropriate here.

Please write back if this does not address your problem.
Julia

******************************************
Julia Koschinsky
Spatial Analysis Laboratory
University of Illinois at Urbana-Champaign
http://sal.agecon.uiuc.edu


-----Original Message-----
From: openspace-bounces at agec221.agecon.uiuc.edu
Behalf Of Michael Anyadike-Danes
Sent: Monday, September 20, 2004 10:32 AM
To: openspace at agec221.agecon.uiuc.edu
Subject: [Openspace] quantile plot


I have a dataset with 434 observations.

I requested a quantile map with 5 divisions (ie a quintile map).

The map has five divisions: "1st range (0); 2nd range (165); 3rd range (87);
4th range (95); 5th range (87)".

I was expecting 5 more-or-less equal ranges (86 and/or 87).

Have I missed something?

Michael Anyadike-Danes
Economic Research Institute of Northern Ireland