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st: Standardization of Ordinal Variables and Polychoric PCA for Index

From   "Hisako Kobayashi" <>
To   <>
Subject   st: Standardization of Ordinal Variables and Polychoric PCA for Index
Date   Tue, 23 Jun 2009 23:14:33 -0700

Dear Statalist:

I want to know how to develop an index from 5 ordinal variables. But I am not sure about standardization of ordinal variables and how to use weights to develop an index.  The ordinal variables are in Likert scale from 1 to 4. 

I am thinking of using eigenvectors of the first component of polychoric PCA (with code of 'polychoricpca').  I believe that this code is for ordinal variables so that I don't need to standardize the variables before I run polychoric PCA. ( Before I run polychoric PCA, I checked Kendall tau b and MCA.).

But after that, I think that I need to standardize ordinal variables to calculate the index with weights (eigenvectors). If so, how can I standardize ordinal variables? And then I multiply each variable by weight from the pca and sum up to make an index.  

I want to know if this procedure is correct or not. This index is one of explanatory variables. I just want to know a simple method to develop an index.

Thank you very much for your help in advance.
Best regards,


Hisako Kobayashi
Ph.D Candidate in Public Administration
School of Policy, Planning and Development University of Southern California

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