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Posted By: cletus What does 2 std deviations mean? - 05/04/10 02:47 AM
One of the criteria for our school's gifted program is that a child's score (in all three categories) on the CogAT must be at least two standard deviations from the mean.

Can anyone tell me what that means or what an example score that's 2 std dev. from the mean would be?

Or is this a score that changes every year depending on the kids taking the test? If so, a ballpark number would help me.

Thanks!
Posted By: no5no5 Re: What does 2 std deviations mean? - 05/04/10 02:54 AM
2 standard deviations above the mean is a typical definition for giftedness. The CogAT has a standard deviation of 16, so 2 SD from the mean would be 132.

The thing that worries me is that this score must be achieved in all 3 categories. That's troublesome because many gifted kids, including some highly gifted kids, aren't gifted in all areas.
Posted By: Val Re: What does 2 std deviations mean? - 05/04/10 03:11 AM
Two standard deviations above the mean on an IQ test means that a person got a higher IQ score than 98% of the population would be expected to get (98th percentile). On the Cogat, the mean is set at 100, and each SD, as nono5 pointed out, is 16 points.

One standard deviation above the norm corresponds to the 86th percentile (116). Three standard deviations corresponds to the 99.9th percentile (148).

These numbers work in reverse, too. One standard deviation below the norm is at the 14th percentile (84); two is the 2nd percentile (68), and three is the 0.1th percentile (52).

HTH,

Val
Posted By: cletus Re: What does 2 std deviations mean? - 05/04/10 03:37 AM
Thanks!

And I should have mentioned this is not the criteria for our district's regular gifted program (in which you qualify for either the math or literacy programs -or both-based on scores) but for their magnet program for the upper 2%. For that program you need to score well in all three categories of the CogAT.
Posted By: knute974 Re: What does 2 std deviations mean? - 05/05/10 04:21 PM
Will they take any alternate testing? Under your district's policy my HG kid wouldn't qualify. MY DD scored a 149 on WISC-IV (99.9th percentile) and 99th percentile on the Naglieri but she only scored above the 98th percentile in one area on the CoGat. As many people on this forum have discussed, CoGAT is a group administered achievement test. It can miss a lot of kids.
Posted By: Val Re: What does 2 std deviations mean? - 05/05/10 04:56 PM
Originally Posted by knute974
Will they take any alternate testing? Under your district's policy my HG kid wouldn't qualify. MY DD scored a 149 on WISC-IV (99.9th percentile) and 99th percentile on the Naglieri but she only scored above the 98th percentile in one area on the CoGat. As many people on this forum have discussed, CoGAT is a group administered achievement test. It can miss a lot of kids.

The gifted program I attended as a kid had two tests. The first one was a group test, and then people who got passing or borderline scores were re-tested individually with a psychologist.

That said, those days are probably gone.

I suppose the answer to your question is "It depends." If the school gets more money for gifted students, then they might be willing to take other scores. If not, it would be a harder argument.

Schools have their own unique rules, I guess. It's odd to think that a school might discount a score of 149 on one of the major IQ tests in favor of a group test. Oh well.

Val
Posted By: Val Re: What does 2 std deviations mean? - 05/05/10 09:52 PM
Originally Posted by gratified3
Those days are still here in some locations. My kids' school did exactly this process (local public elementary). There was a screening process followed by full WISC (and if old enough, WIAT) testing. GT was >130 on WISC but GAI was also accepted.

Wow! That's great. I'm envious of your district already.

Val
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