Showing posts with label Wechsler batteries. Show all posts
Showing posts with label Wechsler batteries. Show all posts

Thursday, July 31, 2014

WJ IV update: WJ IV g-scores (GIA,BIA,Gf-Gc composite) correlations with WISC-IV/WAIS-IV FS and GAI IQ scores

In the WJ IV technical manual (McGrew, LaForte, Schrank, 2014) concurrent validity results are presented for the WJ IV COG with the WISC-IV and WAIS-IV (click here for WJ IV COG overview and select correlation information from tech. manual).

A number of psychologists have asked about correlations between the primary WJ IV COG g-scores and the Wechsler General Ability Index (GAI).  They are not presented in the technical manual.  I have now computed those correlations, as well as a few others with the Wechsler GAI, and they are now part of the SlideShare at the link above and are also reported below.  Click on image to enlarge.

Monday, September 02, 2013

The Wechsler Arithmetic subtest measures quantitative reasoning...another study

A new study on the now "old" WISC-III which still provides insights into the debate regarding what the Wechsler Arithmetic subtest measures. Consistent with research I have coauthored and my analysis of other studies (click here to view), this new study is consistent with the classification of Arithmetic as primarily a measure of quantitative reasoning.

Click on images to enlarge.

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Friday, July 06, 2012

Research byte: WAIS-IV Visual Puzzles study

Click on image to enlarge

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Research bytes: WAIS-IV practice effect study

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Roberts et al (2005) on Wechslers, WJ III and CHC theory

From the above excellent book. See select comments about the Wechslers, WJ III and CHC theory by Roberts et al. - a very good chapter in an excellent book.

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Monday, April 02, 2012

CHC theory and the Wechsler IQ scales and test development

In 1998 Dr. Dawn Flanagan and I published the Intelligence Test Desk Reference book which was the first thorough treatment of CHC theory (then called Extended Gf-Gc theory). This book is now out-of-print.

We then took the concepts from the ITDR and, together with Dr. Sam Ortiz, presented a cross-battery approach to interpreting the Wechsler batteries.

And again, this book is no longer in print. This also means we no longer receive any $ for sales (conflict of interest disclosure). Table of contents for first three chapters below (click on images to enlarge)

The research, theory, and conceptual material in the second book is nearly identical to the first, but it was presented in the context of how to upgrade interpretation and understanding of the Wechsler batteries according to the CHC framework. Since then the same CHC overview material has been tweaked and updated in a series of CHC cross-battery books by Flanagan et al. But, the foundation of CHC theory, and how it can be integrated within a conceptual framework of test development and interpretation, is largely the same in these newer CHC cross-battery books.

Thus, given that these "mother and father" books are no longer in print, I took the liberty of copying the first three chapters of the Wechsler oriented book and am now making them available for my readers (click here). I make this material available to provide psychologists who have not done much reading regarding CHC theory an opportunity to have access to the basic foundation of CHC theory to help them see how it can be applied to the interpretation of an intelligence battery (in this case the Wechslers). By choosing the Wechsler material this also helps understand how the Wechsler batteries are evolving (either implicitly or explicitly--see Keith and Reynolds, 2010) when viewed from the lens of CHC theory.

But, one must recognize that this material is a bit dated. An update of CHC theory was later published in 2005 (click here to some other chapters), and was again updated this year by Schneider and McGrew (click here).

However, the CHC chapter I provide in this blog post, particularly when placed in the context of the Wechsler batteries, provides a solid foundation for understanding CHC theory and its impact on contemporary intelligence test development and interpretation. My goal is to increase awareness of CHC theory and its relevance to psychological assessment and interpretation. My goal is to spur others to become more current re: this now dominant framework in the field of applied IQ testing.

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Wednesday, September 21, 2011

More support for CHC interpretation of the WAIS-IV

(double click on images to enlarge)

Yet another CFA study of the WAIS-IV standardization data that suggests the CHC framework is likely the most vablid interpretative framework for the WAIS-IV. Other posts in support of this conclusion can be found here and here.

Of particular note is the continued finding, consistent with my interpretation of the literature that the Arithmetic subtest is a factorially complex and mixed measure of 2-3 different CHC domains and thus, should NOT be interpreted as a strong indicator of any particular CHC domain. This does not mean it is a bad test. On the contrary, factorially complex tests are sometimes some of the best predictors of other outcomes because they measure multiple abilities (which makes them function as mini g-proxies). The point, reinforced by this latest study, is that Arithmetic is not a good strong indicator of a single CHC domain and has considerable construct irrelevant variance when interpreted within a CHC framework

Conflict of interest note - I am a coauthor of the WJ III which is a competitor to the WAIS-IV

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Friday, September 09, 2011

The factor structure of the French WISC-IV: Dr. Philippe Golay presentation

Thanks to Dr. Philippe Golay for sharing a copy of a poster presentation ("Revisiting the factor structure of the French WISC-IV: Insights through Bayesian structural equation modeling (BSEM)" he is presenting Monday at the 12th Congress of the Swiss Psychological Society.

Double click on image to enlarge and click here for PDF copy of the poster.

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Tuesday, June 28, 2011

Special issue of Assessment journal on the WAIS-IV and WMS-IV research

The journal Assessment just published a special issue on the WASI-IV/WMS-IV. I love the journal cover (see above)

Frazier, T. W. (2011). Introduction to the Special Section on Advancing WAIS-IV and WMS-IV Clinical Interpretation. Assessment, 18(2), 131-132.

Bowden, S. C., Saklofske, D. H., & Weiss, L. G. (2011). Augmenting the Core Battery With Supplementary Subtests: Wechsler Adult Intelligence Scale-IV Measurement Invariance Across the United States and Canada. Assessment, 18(2), 133-140.

Brooks, B. L., Holdnack, J. A., & Iverson, G. L. (2011). Advanced Clinical Interpretation of the WAIS-IV and WMS-IV: Prevalence of Low Scores Varies by Level of Intelligence and Years of Education. Assessment, 18(2), 156-167.

Drozdick, L. W., & Cullum, C. M. (2011). Expanding the Ecological Validity of WAIS-IV and WMS-IV With the Texas Functional Living Scale. Assessment, 18(2), 141-155.

Gregoire, J., Coalson, D. L., & Zhu, J. J. (2011). Analysis of WAIS-IV Index Score Scatter Using Significant Deviation from the Mean Index Score. Assessment, 18(2), 168-177.

Holdnack, J., Goldstein, G., & Drozdick, L. (2011). Social Perception and WAIS-IV Performance in Adolescents and Adults Diagnosed With Asperger's Syndrome and Autism. Assessment, 18(2), 192-200.

Holdnack, J. A., Zhou, X. B., Larrabee, G. J., Millis, S. R., & Salthouse, T. A. (2011). Confirmatory Factor Analysis of the WAIS-IV/WMS-IV. Assessment, 18(2), 178-191

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Sunday, March 27, 2011

IAP Applied Psychometrics 101 Report #10: "Just say no" to averaging IQ subtest scores

Should psychologists engage in the practice of calculating simple arithmetic averages of two or more scaled or standard scores from different subtests (pseudo-composites) within or across different IQ batteries? Dr. Joel Schneider and I, Dr. Kevin McGrew say "no."

Do psychologists who include simple pseudo-composite scores in their reports, or make interpretations and recommendations based on such scores, have a professional responsibility to alert recipients of psychological reports (e.g., lawyers, the courts, parents, special education staff, other mental health practitioners, etc.) of the potential amount of error in their statements when simple pseudo-composite scores are the foundation of some of their statements? We believe "yes."

Simple pseudo-composite scores, in contrast to norm-based scores (i.e., composite scores with norms provided by test publishers/authors--e.g., Wechsler Verbal Comprehension Index), contain significant sources of error. Although they have intuitive appeal, this appeal cloaks hidden sources of error in the scores---with the amount of error being a function of a combination of psychometric variables.

IAP Applied Psychometrics 101 Report #10 addresses the psychometric issues involved in pseudo-composite scores.

In the report we offer recommendations and resources that allow users to calculate psychometrically sound pseudo-composites when they are deemed important and relevant to the interpretation of a person's assessment results.

Finally, understanding the sources of error in simple pseudo-composite scores provides an opportunity for practitioners to understand the paradoxical phenomenon frequently observed in practice where norm-based or psychometrically sound pseudo-composite scores are often higher (or lower) than the subtest scores that comprise the composite. The "total does not equal the average of the parts" phenomenon is explained conceptually, statistically, and via an interesting visual explanation based on trigonometry.


The publishers and authors of intelligence test batteries provide norm-based composite scores based on two or more individual subtests. In practice, clinicians frequently form hypotheses based on combinations of tests for which norm-based composite scores are not available. In addition, with the emergence of Cattell-Horn-Carroll (CHC) theory as the consensus psychometric theory of intelligence, clinicians are now more frequently “crossing batteries” to form composites intended to represent broad or narrow CHC abilities. Beyond simple “eye-balling” of groups of subtests, clinicians at times compute the arithmetic average of subtest scaled or standard scores (pseudo-composites). This practice suffers from serious psychometric flaws and can lead to incorrect diagnoses and decisions. The problems with pseudo-composite scores are explained and recommendations made for the proper calculation of special composite scores.

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Sunday, February 20, 2011

Research brief: WAIS-IV US-Canadian factor and score comparability

The transportability of the meaning of an intelligence test batteries composite scores across countries/cultures is important when a test is originally developed and normed in one country and is then adapted and used in a second country.

Bowden et al (2010) recently investigated the factorial invariance of the WAIS-IV across US and Canadian samples. The results are summarized in the abstract below (click to enlarge). The WAIS-IV was found to measure the same theoretical constructs across the two countries. However, the reported difference in latent mean factor intercepts indicated that the WAIS-IV provides higher scores with Canadian subjects. The need for Canadian norms are suggested.

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Monday, January 31, 2011

IQ test "practice effects"

A practice effect is a major psychometric issue in many Atkins cases, given that both the state and defense often test the defendant with the same IQ battery (most often a Wechsler), and often within a short test-retest interval. Click here to view all ICDP posts that mention practice effects.

Dr. Alan Kaufman has summarized the majority of the literature on practice effects on the Wechslers. He published an article in The Encyclopedia of Intelligence (1994; Edited by Robert Sternberg) that summarized the research prior to the third editions of the Wechsler scales. That article is available on-line (click here).

The most recent summary of the contemporary Wechsler practice effect research is in Lichtenberger and Kaufman (2009) Essentials of WAIS-IV Assessment (p. 306-309). The tables and text provide much about WAIS-IV and some about WAIS-III. The best source for WAIS-III is Kaufman and Lichtenberger, Assessing Adolescent and Adult Intelligence (either the 2002 second edition or the 2006 third edition), especially Tables 6.5 and 6.6 (2006 edition). Below are a few excerpts from the associated text from the 2006 edition

"Practice effects on Wechsler's scales tend to be profound, particularly on the Performance Scale" (p. 202)

"predictable retest gains in IQs" (p.202)

"On the WAIS-III, tests with largest gains are Picture Completion, Object Assembly, and Picture Arrangement"

"Tests with smallest gains are Matrix Reasoning (most novel Gf test), Vocabulary and Comprehension

Block Design improvement most likely due to speed variance--"on second exposure subjects may be able to respond more quickly, thereby gaining in their scores" (p. 204)

One year interval results in far less pronounced practice effects (p. 208).

"The impact of retesting on test performance, whether using the WAIS-III, WAIS-R, other Wechsler scales, or similar tests, needs to be internalized by researchers and clinicians alike. Researchers should be aware of the routine and expected gains of about 2 1/2 points in V-IQ for all ages between 16 and 89 years. They should also internalize the relatively large gain on P-IQ for ages 16-54 (about 8 to 8 1/2 points), andn the fact that this gain in P-IQ swindles in size to less than 6 points for ages 55-74 and less than 4 points for ages 75-889" (p. 209).

"Increases in Performance IQ will typically be about twice as large as increases in Verbal IQ for individuals ages 16 to 54" (p. 209)

Finally, the latest AAIDD manual provides professional guidance on the practice effect.

"The practice effect refers to gains in IQ scores on test of intelligence that result from a person being retested on the same instrument" (p. 38)

"..established clinical practice is to avoid administering the same intelligence test within the same year to the same individual because it will often lead to an overestimate of the examinee's true intelligence" (p. 38).

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Monday, January 24, 2011

The KAIT Gf-Gc IQ test: An under-appreciated contribution to the evolution of CHC intelligence theory

I have been busy revising my 2005 book chapter on CHC Theory: Past Present and Future. It is now coauthored with Dr. Joel Schneider who took the lead and is now first author. Together Joel and I wrote WAY toooooooo much material, and we had to do some serious editing...dropping major sections that we thought were important. I have decided that some of those sections that I wrote would appear hear at IQs Corner, and possibly in future manuscripts yet to be determined.

Part of the chapter is a visual-graphic presentation, with narrative text, of the CHC Timeline project I've been working on for a few years. If you visit the timeline link you will also gain access, via links, to the original chapter, which will provide you more context.

Cut from the submitted draft were comments about the under-appreciated role of KAIT IQ test in the evolution of Gf-Gc/CHC assessment instruments. You can see this event in the timeline at the link above. Below is the text written to explain the small, yet important, contribution of the KAIT to the evolution of CHC theory. Although I wrote most of this section, there are a few well crafted sentences below that were written by Joel.

The contribution of the KAIT Gf-Gc test to the evolution of CHC theory and assessment

An under-appreciated contribution to the evolution of Gf-Gc intellectual assessment was the publication of the Kaufman Adolescent and Adult Intelligence Test (KAIT) (Kaufman & Kaufman, 1993), based on Cattell’s (1941, 1943) original gf-gc Theory instead of the Horn–Cattell (1966) Extended Gf-Gc Theory. The Kaufmans used the older theory not out of ignorance but for pragmatic reasons (and some admirably subtle theoretical justifications as well). However, the distinction between the older, broader, and deliberately multidimensional gf and the newer, narrower, and more unidimensional Gf (as reflected Extended Gf-Gc theory) was probably lost on most potential users of the test.

By self-admission, Kaufman (2009) noted that the KAIT “sadly, has been all but ignored in the United States” (p. 1). The failure of the KAIT to attract assessment professionals was most likely due to the dominance of the venerable adult Wechsler batteries and bad timing. The trend in test development was moving toward giving users the option to measure narrower abilities with more factor-pure subtests and the KAIT was out of step with this trend. Flanagan and McGrew’s (1998) joint KAIT/WJ-R CFA presented an eight-factor Extended Gf-Gc model (Gf, Gc, Grw, Glr, Gsm, Ga, Gv, Gs) and suggested that the KAIT Gf composite, by the standards of the Extended Gf-Gc Theory, was a mix of Gf, Gsm, Gv, and Glr. The decision to measure the older, broader gf was not wrong (indeed, other tests have composite scores with comparable ability mixtures such as the WJ-III Thinking Abilities composite, CAS Full Scale IQ, KABC-II Mental Processing Composite, DAS-II Special Nonverbal Composite, or the now-discarded PIQ from the Wechsler series). The problem was that only the Gf and Gc constructs were represented by at least two KAIT tests and thus there was no option to form reasonably unidimensional composite scores.

​The small KAIT blip on the Gf-Gc assessment radar screen was important for a number of reasons. First, Alan Kaufman’s opinion carries weight in this field. When he recognized the importance of Gf-Gc theory (first in the publication of the original K-BIT, which is now in its second edition), other test developers noticed. Post-KAIT publication Kaufman and colleagues began an active program of Gf-Gc research and publication (see Kaufman, 2009) that foreshadowed Kaufman’s embracing of CHC theory as the consensus model of intelligence for use in the development of intelligence batteries (Kaufman, 2009). Second, it was during their WJ-R/KAIT CFA study that Flanagan and McGrew (1998) recognized that all Gf-Gc assessment research up to that point in time had myopically focused exclusively on the broad Gf-Gc domains, ignoring the importance of understanding individual tests as per the narrow (stratum I) abilities they measured.

I would not be surprised if the KAIT, or parts of the battery, reappear in some form of cognitive assessment instrument(s) in the future.

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