Which is a "true IQ"? If someone were to ask me what my child's IQ score is, would I say the FSIQ or the GAI? Specifically I am referring to the WISC IV, and there is a difference (12 points) between the two scores.
Also, when extended scoring is used, can the GAI go above 160?
FSIQ includes measures of working memory and processing speed, neither of which is highly correlated with general intelligence, "g", but both of which can affect real-world functioning in significant ways. GAI only includes reasoning ability measures, which are the best measure of "g". According to the technical guidance, in general, when there is a significant difference between FSIQ and GAI, the GAI should be taken as the more accurate representation of intelligence, provided that there is not also a significant difference between PRI and VCI. (If the index scores - VCI, PRI, WMI, and PSI, - are significantly discrepant from each other, they obviously can not be combined into a valid composite - not that this stops some people from trying...)
aculady - yours is one of the best answers to that question that I have heard. Thank you!
Aculady, here's something I've never understood. Even if the scores aren't 'significantly' lower, why shouldn't the GAI still apply? If seems to give the kid with the bigger gap, the higher IQ if only one of the kids has the gap. Lower scores in other areas will bring down everyone's scores, not just those with large gaps.
I guess I would agree that for the gap kid, the GAI is more accurate than the the FSIQ. But this GAI isn't more accurate than another kid's FSIQ, is it? I worry when scores get compared, and unfortunately they often do. One kid could miss a GT cut for their FSIQ while another makes it with the same GAI score, when the only difference is the latter child has lower memory/speed scores.
Memory and processing scores that aren't significantly different from VCI and PRI shouldn't lower FSIQ significantly. A difference of as few as 6 points between FSIQ and GAI is considered "significant". That said, GAI is certainly the appropriate composite to use for gifted program admissions. 40% of children identified as G/T had FSIQ 5 points less than GAI. If WMI and PSI are low enough to affect performance, appropriate accommodations may be needed.
These links are relevant:
http://www.ksde.org/Portals/0/Special%20Education%20Services/gifted/WISCIVTechReport4.pdfhttp://www.nagc.org/index.aspx?id=2455
"More accurate" and "true IQ" are themselves rather meaningless terms. There is no "perfect" number tatooed in the kid's genes, and the tendency to assume that the highest number is necessarily the "most accurate" is itself a misconception.
The GAI is one measure of general intelligence, which de-emphasizes the role of working memory and processing speed.
The FSIQ is another measure of general intelligence -- and it is not, by the way, a true statement that WM and PS have nothing to do with general intelligence. Both scores can be valid -- they are just measuring different things.
If we used a different test entirely, we'd get yet a different measure of general intelligence. You cannot separate the score from the test used to generate it.
As for the statements about statistical significance, note that in most cases, the number of points different for statistical significance at the p<.05 level is considerably higher than cited above, particularly when one makes the comparison to the segment of the norming sample with similar overall performance. Also, recognize that just because a difference is statistically significant, that does not necessarily mean that it is particularly uncommon in the population, nor does it necessarily mean that it is clinically significant for that particular individual. That kind of analysis should be done on a thoughtful and individual basis.
What research indicates about identification procedures is that you should match the identification procedures to the intervention programs. That is, if the program is going to require a kid to do stuff that relies on WM and PS, don't use GAI for identification, because you're going to end up getting kids in the program who then can't handle the work, and you're going to exclude kids who should be in the program. This is most notable with the trend to use nonverbal fluid reasoning tests to identify kids for programs with high verbal written output requirements... a recipe for frustration on all sides.
What research indicates about identification procedures is that you should match the identification procedures to the intervention programs. That is, if the program is going to require a kid to do stuff that relies on WM and PS, don't use GAI for identification, because you're going to end up getting kids in the program who then can't handle the work, and you're going to exclude kids who should be in the program. This is most notable with the trend to use nonverbal fluid reasoning tests to identify kids for programs with high verbal written output requirements... a recipe for frustration on all sides.
Is the Naglieri Nonverbal Ability Test (NNAT) an example of such a nonverbal fluid reasoning test?
