Gifted Issues Discussion homepage Forums Identification, Testing & Assessment WJ III Ach Question

OP has erased scores (understandably), but this comment makes it clear something is amiss, as it seems to be in the other thread.
http://giftedissues.davidsongifted...._Broad_Scores_calculatio.html#Post188503

I never found anyone who was able give me any answers, only speculation. I erased the previously posted scores for privacy reasons.
However I do have a consultation with a psychologist this weekend who may be able to shed some light on our questions. I will be sure to update with any information I get.

Well, I'd love to say I had some answers to our questions, but the psych wasn't able to provide any perspective. Hopefully someone else has something to share

Just to clarify: was it actually the RPI or the standard score that was peculiar? (I'm coming to this thread late, so I didn't see your scores when they were up.) The RPI is a very different measure from the standard score, and is not easily compared across subtests, due to the differences in the way different academic and cognitive skills progress in the general population.

aeh,
My question has been how could the broad and brief reading scores be so different. But more importantly how could the broad reading RPI be 6 points lower then the lowest subset score, given that the AE and GE (though I didn't include it) are basically on par with all the rest of the scores. DD's results are below. She was tested at 4yrs 10mo.

Test/W/AE/RPI/SS
Broad Reading xxx
Brief Reading xxx

Test/Raw/W/AE/RPI/SS
Letter-Word ID xxx
Reading Fluency xxx
Passage Comp xxx
Word Attack xxx
I think these were all the subsets included to calculate both the broad and brief scores.

Thank you for taking the time to even look

So, no guarantees that this is the explanation, but I'll throw a few thoughts and general guidelines out there.

First, a couple of little housekeeping items: some of your columns are reversed; the column with the 100/90s is actually the RPI, and the previous column, that puzzles you, is the standard score. The SS is a deviation measure, comparing your performance to an age-normative group in a rank order manner (related to percentile). The RPI compares how challenging tasks might be expected to be. It has a very low ceiling, as the second 90 represents the level at which the median peer would be expected to be 90% successful. On that task, your student would be predicted to be the first number % successful (in this case, 98 to 100%).

Second, Broad Reading is derived from LWI, RF, and PC. Brief Reading omits RF. WA only comes into the Basic Reading Skills cluster, which you have not reported.

Now we get to the odd part of things. Deviation scores (SS, in this case) represent both the distance from the norm, and the rank order in which a test performance occurs in the norm population. When you start combining performances (i.e., subtests) to form composites (i.e., cluster scores), sometimes they don't come out the way you would expect. I'll name two factors that often play into this:

1)The likelihood of any given person having an unusually high score in one isolated area (a splinter skill, as it were), is actually much higher than one would think from a common sense standpoint. What's really unusual is scoring in that same high range across the board. So the cluster/composite score derived from two 150s might be expected to be higher than that derived from a 160 and a 140, as it was a rarer occurrence in the norm population, even though the mean score of both is 150. Not all tests derive their composite scores this way, and, to be honest, I can't remember if the WJ is one of them, but it is possible that this is the case.

2) Out at the extremes of the norm group, there are fractional individuals representing these standard scores in the actual norming population, so test developers have to use statistical smoothing methods to estimate standard scores. (If you have 2000 people in your norm group--which is considered a pretty good size--and your norms are divided into, let's say, three groups per year for school-age children, this results in roughly 50-60 children per group, which means that one child is representing the entire top 2% of the population. You can see how imprecise this is for the extremes of the bell curve.) Now, the statistical estimation methods are better than one would expect, but still, once you get out beyond three or four standard deviations from the mean (145+), it's not very well connected to the actual standardization sample.

For your child, there is a pretty wide range among the subtests feeding into the cluster scores, so it is possible that either or both of these factors were involved.

aeh, I just wanted to let you know I sent you a private message.

Test/W/AE/SS/RPI (corrected )
Basic Reading Skills xxx

So given the basic reading and the brief reading are "closer" I guess it still boggles my mind how the broad SS score can be so far off even given your explanation below, not that I doubt what you are noting however. I guess I would expect to see appropriate decrease in AE and GE to reflect the lower SS score not the same AE and GE and a 28-38 point SS difference YKIM?

Thank you for taking the time to look at her scores, I really do appreciate it!

Well, the AE and GE not lining up with the SS across subtests is an easy one. Different skills progress at different rates, and also reach their ceilings at different ages. Some have "plateaus" during certain age ranges, and steep growth curves during other age ranges. If you think about this a little, it also follows that, at certain ages, a point or two difference in the raw score can have a dramatic impact on the scaled/standard score, whereas at other, "denser" ages, a larger raw score difference can have negligible impact on the SS.

If I recall correctly, your child was also very young at the time this was administered, (preschool-age, right?) which means there is the additional factor that the average child (the majority of the norm group) has not even been exposed to academic skills that your child appears to have advanced fairly far in. So even fewer children than at some other age-norm levels were the basis of the statistical extrapolation that generated these SSs.

I'm not going to claim I can explain it all...

In the bigger picture, all of these oddities are part of why very early testing cannot be considered stable.

Regardless, it is clear that you are blessed with a child with great abilities. Enjoy!