Originally Posted by geofizz
OK, geeked out on DS' WJ scores.

Grade 4.4 norm: GE is broadly linear over 78 SS point variation with a decent quality of fit. Residuals between ±1.5 GE (furthest above the fit line is Applied Problems; furthest below is writing fluency)

Grade K.6 norm: GE also broadly linear over 50 SS point range. Residuals +1.1/-0.6 (Picture Vocabulary and Spelling).

Note that DS is about to come out with a dyslexia diagnosis.

All of this, of course, says nothing of his IQ, which does not have nearly the point spread as the achievement, none of which would quantitatively predict either the highs or lows of achievement.
On the geek theme--a little light reading on norm construction, re-weighting, curve smoothing, with an example of a section of the age equivalent curve for one subtest:
http://www.riverpub.com/products/wjIIIComplete/pdf/WJIII_ASB9.pdf

Technical data on standardization; look on p. 17 for smoothed curves for major clusters, by age:
http://www.riverpub.com/products/wjIIIComplete/pdf/WJIII_ASB2.pdf
Not much detail, but it gives you an idea.

...pronounced like the long vowel and first letter of the alphabet...