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Re: st: cluster analysis validation

From   "Dasinger, Lisa" <>
Subject   Re: st: cluster analysis validation
Date   Mon, 23 Apr 2012 11:45:04 -0700

Paul -  Thank you for your response.  I have been using -cluster
wardslinkage-, which produces the same result as long as the same
dataset is used.  It sounds like you are talking about kmeans.  In any
case, I will look into your program as it may also be helpful here.


Date: Thu, 19 Apr 2012 17:41:56 -0400
From: Paul Millar <>
Subject: Re: st: cluster analysis validation


Cluster analysis is empirical - the group assignments are based on
minimizing the "distance" between cases, given the number of groups.
So a different sample entails different groups.  If you run cluster
analysis many times on the same data you will also get different
results for the same data (because the starting case is different,
assigned randomly using -set seed-).  I have written a routine that
tests the reliability of a groups assignment by sampling the group
assignments and then estimating whether the probability of assignment
in a particular group is > 0.5 in the population of group assignments.
 See -help clustpop- after -ssc install clustpop-

You can also do this after pooling the data, as suggested earlier.

- - Paul

Lisa Dasinger, Ph.D.
Data Reporting Manager
Claims Analytics
Zenith Insurance Company
Pleasanton Regional Office
4309 Hacienda Drive, Suite 200
Pleasanton, CA 94588
Phone: 925.416.5235
RightFax: 925.460.1235
Branch: 925.460.0600

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