My son is 19 years old and intellectually disabled. We applied for SSI for him and they are requiring him to take another IQ test. He took one at age 10 (Full IQ = 56, subsets ranging 55-72) and another at age 13 (Full IQ = 50, subsets ranging 55-62). Both were WISC-III. Now he will be taking the WAIS-IV and my question is, how closely will the WISC numbers correspond to the WAIS? I know that IQ is a fluid, not an absolute number, but I want to know some generalizations so if the examiner comes up with an out-of-left field number, I can dispute it. Thanks.
The correlation between the two tests is very good in the studies — with a score of 1.00 being perfect the correlations run about .90. This means that the chances are very good that the WAIS score will be reasonably close to the other scores obtained.
Testing on the WAIS is typical when a disability claim is filed. If the number is off by more than 10-15 points from the last test and you want to dispute it you may want to consult with a lawyer familiar with SSDI to learn about your son’s rights.
Tomasulo, D. (2013). IQ Testing. Psych Central. Retrieved on April 28, 2015, from http://psychcentral.com/ask-the-therapist/2013/10/28/iq-testing/