Gifted Issues Discussion homepage Forums Identification, Testing & Assessment Cogat percentiles

I am hoping someone here can help me...I've tried Google for a bit but haven't found an answer yet. Our school just sent us Cogat scores, but the report shows only the percentile rank within each category, not the scaled score. Is there a way to figure out the scaled score (or at least the range) from the percentile rank? We can obviously ask the school for a more comprehensive report, but it's Friday evening and this just has me wishing we had more information...

thank you!

I think that the CogAT uses a normal curve with a mean of 100 and a SD of 15, like most IQ scales. If that is correct, you can use http://www.measuringu.com/zcalcp.php to convert the percentile into a Z-score (choose one-sided for the proportion of area). Multiply the Z-score by 15 and add 100 and you should get the scaled score. So, for example, a percentile of 98% gives a Z-score of 2.05, which converts to a scaled score of 2.05*15+100=131.

I think the CogAT is a standard deviation of 16. I remember checking into this because the WISC standard scores/percentiles didn't match up with the CogAT standard scores/percentiles. So if a kid gets 99th percentile on the CogAT, it would be a higher standard score than they would have with the same percentile on the WISC. Our school district required a CogAT score of 139 or something, but we were using outside WISC scores and it's harder to get that on the WISC....they are not exactly comparable. A 139 on the CogAT was like a 136 or 137 on the WISC.

Yes. CogAT has an x of 100, and SD of 16. Use the percentiles if you want to compare to WISC scores.

Thank you for the helpful info. How is the composite score derived? My DS's composite is 99% even though only one of his subtest scores is 99...

I think that's pretty common. It's sufficiently unusual to do well on all the subtests that you can get a 99th %ile even when you don't score in the 99th on any subtest.

On the CogAT, DD had only one 99% subtest, but a 99% composite, as well. I concluded that she probably scored a pretty high 99% on that subtest.

FWIW, this breakdown really predicted her later WISC subtests (CogAT Verbal probably a "high 99%; WISC VCI was extremely high). I know that this is not true for everyone, though.