Gifted Issues Discussion homepage Forums Identification, Testing & Assessment cogAT results question

I have a question about the cogAT test. Just wandering what was the difference in the Age and Grade percentile ranks for your kids. I read that it's usually nearly identical, or 1-3% difference for a typical age student in a particular grade. My daughter was 8.2 yo at the time of testing, and is in 2nd grade. Her grade percentile ranks were V-72, Q-90, NV-91, and composite 89 and her age percentile ranks were V-60, Q-84, NV-87, and composite 81. Anyway, I'm just trying to figure out why would there be a 12% gap in her verbal, and the other gaps are kinda high too. A friend of my who's daughter is also 8.2 didn't have those gaps, so I'm confused. Thanks in advance!

One possible explanation is that many kids 8.2 yo would be in 3rd grade, therefore her age scores are compared with children who've been exposed to an additional year of classroom material.

DD had just turned 7 when she took the CogAT in second grade, and her age percentiles were only slightly higher than grade. For instance for verbal she may have been at 97th percentile for age but 95th percentile for grade. She took a version of the test that is timed and normally given to third graders, so I'm not sure if that made any difference. It is optional for schools to give kids a higher-level version of the test so that the test ceiling is higher. Her grade scores were compared to other second graders though, not third graders.

DS took the CogAT and the grade and age percentiles were identical. He has a late winter birthday so he is probably middle of the pack in terms of age for his grade. When he took it, he was 7 years, 8 months, I think. It seems a little weird that you are seeing such big differences in terms of the percentiles when I saw very little difference with DD, who was very young compared to most other second graders who were tested (she was grade-accelerated). You might want to try to verify that they didn't make an error with her birthday or grade.

Another factor is the norms being used. Depending on the institution, there may be local norms, as well as national norms. Some local norms will result in higher percentiles for the same raw score, and others will result in lower percentiles for the same raw score. Some districts also have older children on average (more holdouts/redshirting). If your friend's daughter is not in the same district, or is reporting local percentiles to you, the gaps may be different.

Also, percentiles are closer together in certain parts of the curve than in others (+/- 1 standard deviation; the middle of the bell curve). For instance, +1 standard deviation, or a SS of 115 for most tests, is the 84th %ile. +2 SD is the 98th %ile. +3 SD is the 99.7th %ile. So from the mean to the first SD, it's 34 %ile points, while from the first to the second SD, it's 14 %ile points, and from the second to the third, it's a mere 1.7 %iles. The same thing holds on the other side of the curve. Standard scores are equally spaced based proportionately to the standard deviation difference, not the percentiles.

A small and relatively insignificant change in standard scores, then, could result in a much larger change in percentiles, if it occurred between the 20th and 80th %iles (or so), than if it occurred outside them. Notice the biggest drop you reported was V, where both the age and grade scores were inside that window.

ETA: CogAt uses a mean of 100 and standard deviation of 16, not 15 like most other tests, but since we're discussing percentiles, the argument is exactly the same.

Her school used national norms, and my friend's daughter is in the same school.

Thanks for explaining it! I still don't fully understand it, but as long as there's a logical explanation, I'll take it.

This is what I would suspect. In second grade, many kiddos would be younger so the grade & age will reflect that depending on which scores you look at.

As for another student same age, were her scores (not percentiles) different? Then she/he may have scores more aligned to 3rd grade and/or 8 year olds.

My kiddos have not taken the Cogat, but I will say that their scores would likely be the opposite with age percentiles higher than grade because in 2nd grade they would have been 6.9 to 7.6 depending on the time of year it was given.

Make sure you consider that at 8.2, your daughters 'grade' peers could be an older 6 to mid 8. That is quite a spread!

Seconding what aeh said, the less extreme scores (closest to the middle) will show the most difference between age and grade percentiles. I've seen it on my son's percentiles too.

I saw less of a gap between age and grade rank this year because they tested them earlier in the year, so that with a late December birthday he was almost average age to take the test. I wonder if this is also part of the reason why his scores were higher. Maybe he was hitting a bit of ceiling previously - I don't know at what ability level that becomes a concern with the cogat.

DD is on the young-end for grade. She was 7-years-old during all of 2nd grade, and was 8 during 3rd. FWIW, her CoGAT percentiles for composite and verbal scores were identical for grade and age. Her nonverbal and math percentiles were a couple of percentile points higher for age than for grade.

My daughter was 7.3 years when she took CoGAT in 2nd grade. Her composites were identical but the individual percentiles were a tiny bit lower for grade versus age. Since your daughter is on the older end of the scale for grade 2 it makes sense that they would be a little lower for age (comparing her to the older kids). However, it does seem to be a pretty big difference. You should probably check with your school counselor, they may be able to provide more info than you received.