Monday, October 13, 2008

On FSIQ, VIQ & PIQ : A general discussion

(One friend suggested I explain what I'm trying to learn to another person, in hopes that the concepts that I am having a hard time remembering will stick better as I prepare for an important test tomorrow. You, dear readers & friends, get to be those 'persons'. )

The particular Intellectual Assessment/Achievement test that I am becoming proficient at results in a Full-Scale IQ (FSIQ) score, as well as a Verbal IQ (VIQ) and a Performance IQ (PIQ) score. The test contains 14 subtests, half of which fall under the VIQ, and the other half under PIQ. Your VIQ score is indicative of your ability to work with abstract symbols, your verbal memory skills and fluency abilities, as well as the amount of education you have had, and whether you actually benefited from that education. Your PIQ score indicates your ability to work with concrete situations, to work quickly, to integrate perceptual stimuli with motor responses, as well as your visual spatial ability.

If there is a significant difference between your VIQ and your PIQ, there are potential reasons for this. Typical reasons for a higher PIQ are if the test-taker is ESL, or has less education. They may also have a learning disability, some level of autism or mental retardation, and possibly even emotional trauma (though additional background information is needed to support the last possibility). Additionally, a higher PIQ often means the test-taker has low auditory processing and conceptualizing skills, meaning that they have difficulty in understanding auditory directions and putting them into practice. A significantly higher VIQ may indicate the test-taker has a high level of education/schooling, they have a deep fund of knowledge, and they are probably caucasion or mainstream American. A higher VIQ may also indicate some level of a mood disorder such as depression, or right-hemisphere brain damage.

The VIQ score is further broken down into 2 indexes, those being VCI (verbal comprehension index) and WMI (working memory index). Subtests that load onto the VCI include Vocabulary, Information and Similarities. WMI includes the subtests of Letter # Sequencing, Digit Span and Artithmatic. The PIQ score is also broken down into 2 indexes, including POI (perceptual organization) and PSI (processing speed). Subtests that fall under POI include Block Design, Matrix Reasoning and Picture Completion. PSI subtests include Symbol Search and Digit Symbol Coding. The three remaining subtests of Object Assembly, Picture Arrangement and Comprehension do not load onto any index.

Here is a visual representation of how things are connected with the specificity of each subtest:
A few thoughts on calculating the IQ scores...Symbol Search, LNS & Object Assembly scores do not calculate into the FSIQ or the VIQ & PIQ. They may, however, load upon an index score, as seen in Symbol Search loading onto PSI and LNS loading onto WMI. As previously mentioned, Object Assembly does not load upon any index.

A few thoughts on reliability & consistency...As with any assessment test, reliability & consistency is important. The FSIQ has a high split-half reliability of .98, VIQ reliability is .97 and PIQ reliability is .94. VCI has a reliability of .96, POI has a relaibility of .94, WMI has a reliability of .93, and PSI has the lowest reliability of .87. Internal consistency for this intellectual assessment test ranges from the low .70's - low .90's. The subtest with the highest split-half reliability is Vocabulary, which is .91, and the subtests with the lowest split-half reliability include Object Assembly at .7 and Picture Arrangement at .74.

If for some reason a subtest is spoiled, you may substitute the Object Assembly score for Matrix Reasoning, and the LNS score for Digit Span. A person's score may be affected by repeated administrations of this assessment as seen by an increase in the FSIQ, VIQ & PIQ when taken a second time within 1 year. FSIQ may raise 4-4.5 points, while VIQ may be raised by 2.5 points, and PIQ by 6.5 points.

On validity...this intellectual assessment has good content validity, construct validity is high as seen in the way that the Vocab & Block Design scores correlate highly with FSIQ, and has a high criterion validity in that the FSIQ correlates highly with other achievement tests, such as SB-IV & V, WISC III & WIAT.

So...did you learn anything?

Coming up in my next installment of studying, the various subtests, what they measure and their specificities! Aren't you excited??


DeniseMarie said...

Uhm....I learned that this class must be really boring. And lots of acronyms used all together gets confusing really fast.

Molly W. said...

Um, I love you but not this much. :) I just got back from class myself and already feel completely brain dead.

Tims said...

holy cow. my brain hurts.

Sara said...

All I can say is ... working memory = .93!!

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