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st: RE: RE: Getting Negative Alphas

From   "Verkuilen, Jay" <>
To   <>
Subject   st: RE: RE: Getting Negative Alphas
Date   Mon, 17 Nov 2008 13:33:20 -0500

Anderson, Bradley wrote:

>>I've worked with some data like these and have observed similar

Good point! There's no reason to assume that these items make up a
unidimensional continuum, which is what Cronbach's alpha is designed to

In the opinion of most in the psychometric community, Cronbach's alpha
is just an approximate analysis of the factor analysis/IRT you really
should have done.  

>>In short, measures of internal-consistency reliability imply a
measurement model that is probably untenable in this case.

Yes, I totally agree. A good reference is David Streiner and Geoffrey
Norman. Health Measurement Scales, Third Edition, Oxford. 2003. I plan
to use it for my class in the spring as a supplementary reading for
emphasizing understanding, with M. J. Allen and W. Yen (1979).
Introduction to Measurement Theory for the basic technical results. 


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