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Re: st: cluster analysis validation
From
Paul Millar <[email protected]>
To
[email protected]
Subject
Re: st: cluster analysis validation
Date
Mon, 23 Apr 2012 15:10:49 -0400
Lisa,
If your dataset is small, or has certain characteristics, you might
get the same result every time. You are right, the most commonly used
method is kmeans, I have not tried wardslinkage.
- Paul
On Mon, Apr 23, 2012 at 2:45 PM, Dasinger, Lisa <[email protected]> wrote:
>
> 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.
>
> Lisa
>
>
> Date: Thu, 19 Apr 2012 17:41:56 -0400
> From: Paul Millar <[email protected]>
> Subject: Re: st: cluster analysis validation
>
> Lisa,
>
> 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
> [email protected]
>
> www.TheZenith.com
>
>
>
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--
- Paul Millar, Ph.D.
School of Criminology and Criminal Justice
Nipissing University
North Bay, Ontario, Canada
www.paulmillar.ca
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