What analysis do IQ tests use?


New Member
I can't find anywhere what statistical analysis IQ tests (like Weschler scales, BAS, etc.) use.

It is not stated in any of their material (that I can find at least).

I've heard it mentioned that PCA and/or hierarchical factor analysis are used?

I know historically some type of factor analysis was used (and created for) IQ testing but can't find anything for current IQ tests.

Thank you!
As you say there are few details unless you get access to the original books by Wechsler and others. There don't seem to be journal articles on it. I could be wrong but I believe that WAIS was not developed using any form of factor analysis. If you read the history it has been developed and modified over the years from batteries of tests developed for different purposes.

There have however been many CFA studies attempting to analyse the factor structure which you can find by doing a lit. review of CFA and WAIS.


Super Moderator
That's a bit of a vague question. They use lots of analyses in the development and validation procedures (typically test-retest correlations, Cronbach's alpha, EFA, CFA, etc etc), but it differs a bit depending on which IQ test you're talking about. The current WAIS-IV manual includes a whole bunch of content about factor analysis. Getting hold of the manual for the test you're interested in is the best bet, or a review of the test published in a journal article.
The current WAIS-IV manual includes a whole bunch of content about factor analysis.
Yeah, the current WAIS and WISC are very different from the original tests developed by Wechsler, while maintaining the original philosophy, and have become much more factorial and take account of new theories and research such as cognitive neuropsych etc.

This is an interesting read about the history

Boake, C. (2002) From the Binet–Simon to the Wechsler–Bellevue:
Tracing the History of Intelligence Testing, Journal of Clinical and Experimental
Neuropsychology, 24:3, 383-405
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