Gifted Issues Discussion homepage Forums Identification, Testing & Assessment How to calculate GAI?

My son recently took the WISC-IV and he tested with the following scores: <deleted>

The psychologist who did the testing did not calculate a GAI for whatever reason (though she did indicate that the FSIQ was likely underreporting his capabilities).

So I was curious and looked up how to calculate GAI. It appears that there are two methods of doing this: one uses the sum of the VCI and PRI, and the other uses the sum of the six subtests of those indices (his six subtest sum was 101). The subtest sum method seemed to state that it was a superior measure over methods that don't use subtest scores.

Is one method generally more accepted than the other? One method gives him a GAI of <lower score> and the other <higher score>.

George, great scores! That WMI coupled with such high reasoning scores is a great combination! I'd also be asking the tester (or perhaps you can see from results) whether your DS eligible for extended norms (2 or more subtests at 19, and he may have scored additional points beyond, esp. in VCI)? Can you ask your tester to calculate the GAI? If not, perhaps aeh is near...

We had our tester do a GAI and it was higher than the FSIQ. Since the PSI is the lowest score the GAI will likely be higher?

The tester should be able to do a revised report with the GAI if you ask.

Those are great scores indeed! As that working memory is beautiful!

The most widely used method is the sum of the six subtests as described in the WISC-IV Technical Report #4:

http://images.pearsonclinical.com/images/assets/WISC-IV/80720_WISCIV_Hr_r4.pdf

which is the 151 you report for a sum of scaled scores of 101.

Yes, the TR posted by Pi22 is the recommended method of calculating the GAI. The other method was a statistical approximation developed by third parties before Pearson released the official method, which was derived from the actual standardization sample.

The FSIQ
Excellent scores one way or the other. Did he have any 19s among the subtest scores? If there were at least two, that would be reason to look into extended IQ scores.

Thanks, everyone, for the advice and the encouragement! We're still a bit shocked he tested so high, as he seems reasonably normal to us.

Aeh, his only 19 was on the vocabulary subtest. The others were all 16s and 17s.

Just an FYI - a GAI of 145+ on the WISC gets one well on the way qualifying for Davidson Youth Scholars.

Cmguy,

Thanks for the info about DYS. I had been under the impression that he wouldn't qualify on account of his FSIQ being 1 point too low. So GAI can be used instead? Even if so, it still seems like he would be on the "low" end of the program? It seems like its target is for the more profoundly gifted child.

He hasn't taken any achievement tests yet, though we are considering it, mainly because we suspect he may be underachieving.

Just a statistical thought.

This is a more a fact about the shape of the bell curve than anything. If everybody with an IQ of 145 or above is segmented off into a second population. Most of the individuals in that second population will be very near 145. In other words the density becomes rapidly more sparse as you get much higher than 145.