I have a complicated view of cognitive testing. I think that scores by category is useful for specific uses but general IQ is absolutely useless and I have personal experiences that really made me believe that.
I myself have gotten comprehensive cognitive testing (part of adult reasessment) and my scores ranged from 21st-98th%, 5th-93rd%, and 2-16th% based on the category (WAIS4IQ, Academic, Adaptive functioning). this is a huge range and that huge range holds some useful information in the details. but even these are estimates based on limited tests despite their utility.
for example, the 5th grade math skills (which doesnt make sense because Im graduated) compared to >12th grade spelling and reading skills (which does makes sense because Im graduated) was simple clear evidence for a math SLD. the adaptive functioning scores were simple, clear evidence for why I should still be on disability (im autistic) and get other supports before going through my big stack of medical paperwork for details.
but for things like IQ my general score doesnt tell you anything meaningful. if you want to look at the individual cognitive skills it might be useful, but the average doesnt say anything except im "normal". your mental abilities can't be put into one number that's not how brains work.
my brother has gotten tested a couple times throughout his childhood and it has ranged from (im not joking) 79 to 115 based solely on how interested he was in doing the tasks. this has caused him to be treated very differently by schools at different times for no other reason. meanwhile his actual grades are fairly average. none of that makes sense if you take either of his IQ scores as a predictor of his actual abilities.








