Showing posts with label WJ IV. Show all posts
Showing posts with label WJ IV. Show all posts
Thursday, November 15, 2018
Tuesday, February 16, 2016
Why full scale IQ scores are often much lower (or higher) than the part scores? Dr. Joel Schneider on the "composite score extremity effect"
Bingo. There is finally an excellent, relatively brief, explanation of the phenomena of why full scale IQ scores often diverge markedly from the arithmetic average of the component index or subtest scores.
This composite score extremity effect (Schneider, 2016) has been well known by users of the WJ batteries. Why....because the WJ has placed the global IQ composite and the individual tests on the same scale (M=100; SD=15). In contrast, most other cognitive ability batteries (e.g., Wechslers) have the individual test scores on a different scale (M=10; SD=3). The use of different scales has hidden this statistical score effect from users. It has always been present. I have written about this many times. One can revisit my latest post on this issue here.
Now that the WISC-V measures a broader array of cognitive abilities (e.g., 5 index scores), users have been asking the same "why does the total IQ score not equal the average of the index scores?" Why? Because the five index scores are on the same scale as the full scale IQ score...and thus this composite score extremity effect is not hidden. A recent thread on the NASP Community Exchange provides examples of psychologists wondering about this funky test score issue (click here to read).
As per usual, Dr. Schneider has provided intuitive explanations of this score effect, and for those who want more, extremely well written technical explanations.
The WJ IV ASB 7 can be downloaded by clicking here. Although written in the context of the WJ IV, this ASB is relevant to all intelligence test batteries that provide a global IQ score that is the sum of part scores.
Kudos to Dr. Schneider.
This composite score extremity effect (Schneider, 2016) has been well known by users of the WJ batteries. Why....because the WJ has placed the global IQ composite and the individual tests on the same scale (M=100; SD=15). In contrast, most other cognitive ability batteries (e.g., Wechslers) have the individual test scores on a different scale (M=10; SD=3). The use of different scales has hidden this statistical score effect from users. It has always been present. I have written about this many times. One can revisit my latest post on this issue here.
Now that the WISC-V measures a broader array of cognitive abilities (e.g., 5 index scores), users have been asking the same "why does the total IQ score not equal the average of the index scores?" Why? Because the five index scores are on the same scale as the full scale IQ score...and thus this composite score extremity effect is not hidden. A recent thread on the NASP Community Exchange provides examples of psychologists wondering about this funky test score issue (click here to read).
As per usual, Dr. Schneider has provided intuitive explanations of this score effect, and for those who want more, extremely well written technical explanations.
The WJ IV ASB 7 can be downloaded by clicking here. Although written in the context of the WJ IV, this ASB is relevant to all intelligence test batteries that provide a global IQ score that is the sum of part scores.
Kudos to Dr. Schneider.
Click on image to enlarge
Thursday, October 15, 2015
Evolution of the WJ to WJ IV GIA and CHC clusters
Click on image to enlarge.
Long-time users of the various editions of the WJ cognitive battery (WJ, WJ-R, WJ III, WJ IV) know that the battery has continued to evolve over time. Above is a portion of a large table that summarizes the same and different tests included in the GIA (g-score) and broad CHC clusters across editions. The complete table demonstrates that the WJ has not remained static, with each new edition evolving as per research and theory.
The practical benefit of the complete table comes when examiners want to compare scores from similarly named cluster scores across different editions of the WJ--different scores may be due, in part, to different mixtures of tests in clusters across editions. I hope this is helpful.
The complete table can be downloaded here. The table is adapted from a similar table in
Cormier, D., McGrew, K., Bulut, O., Funamoto, A. (2015). Exploring the relationships between broad Cattell-Horn-Carroll (CHC) cognitive abilities and reading achievement during the school-age years, Manuscript submitted for publication.
Monday, February 2, 2015
WJ IV Technical Manual Abstract Asssessment Service Bulleting is now available
A new WJ IV Assessment Service Bulletin (ASB) is now available at the WJ-IV Riverside website. It is a free download. The description at the site is below. Click here to visit the page.
This bulletin provides a summary of the procedures followed in developing and validating the WJ IV.
Throughout the development and design of the WJ IV,
the test standards outlined in the Standards for Educational and Psychological Testing (American
Educational Research Association [AERA], American Psychological Association [APA], & National Council on Measurement in Education [NCME], 2014) were followed carefully.
Information in this bulletin is abstracted from the Woodcock-Johnson
IV Technical Manual (McGrew, LaForte, & Schrank, 2014) and is intended as an overview to highlight important aspects of the WJ IV
test design, reliability, and validity. Readers who are interested in more detailed information should consult the WJ IV Technical Manual.
ASB 1 (WJ IV Tests of Achievement Alternate-Forms Equivalence) is also available for download on the same web page.
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