The problem is that people think "it's a score on an IQ test, it must be comparable to scores on other IQ tests." But it's not even remotely. The current technical bulletin from Riverside literally uses the phrase "apples and oranges." The deal is that if you compare, say, a WISC-IV and an SB-5 IQ, they're measuring somewhat the same thing in somewhat the same way -- they're asking, "how unusual is this child's performance compared to the performance of other children the same age?" The SBL-M is not asking the same question -- it's asking, "what number do we get when we divide the child's age equivalent on this test with his chronological age?" The problems with age equivalents are numerous, too many to go into here (maybe I'll do a series in my blog on test scores and what each score type does and doesn't mean), to the point where professionals are strongly discouraged from using them. And even if you did think that age equivalents had some reliability and validity, they are not actually linear data, nor do they have a true zero -- they are really just ordinal data (you can say "ahead" or "behind" but not how far ahead or behind). Which means that you cannot actually add, subtract (= compare), multiply, or divide (= create ratios) with them. (And all of this is before you even think about the fact that this test was written in 1960 and last renormed in 1972 and is based on an outdated idea of what intelligence is and how to measure it and is culturally biased and so on...)
The bottom line is that a 160 on an SBL-M is not "more accurate" than a 140 on an SB-5. The two scores aren't even measuring the same thing -- it's as if you said, "The kid had a 32 BMI but a 148 lb weight, so the weight is more accurate because it's a bigger number." The scores aren't even comparable -- the scores on the SB-5 are, in fact, compressed towards the mean (as the technical manual for the SB-5 shows). But that doesn't mean that the SB-5 is missing some crucial information that only the super-special SBL-M can show. It means that they are using different measuring systems with different markings on the measuring sticks. It is frankly misleading to suggest otherwise.
And gratified is right -- I literally see eye-rolling from psychologists and educators in response to the L-M. It makes the parents look like the narcissistic pushy parents the professionals might already tend to assume we are.
Frankly, I question not just the possibility with *any* test, but also the *utility* of knowing whether a kid is in the top .1% versus in the top .001% of the population. I don't believe that X test score always means Y intervention will be necessary (I really disagree with professionals who say things like, "Oh, your kid is so smart, he will never be happy in any school.") -- kids are much more diverse than that, and so are interventions. The further you get from the mean, the more the score is dependent not just on what the kid and the tester had for breakfast, but also what Louis Terman, Maud Merrill, David Wechsler, Gale Roid, or whoever else wrote the test had for breakfast -- how the very notion of intelligence was defined and what specific item types and item content were used to measure it.
My husband likes to use the analogy of an "AQ" (athletic quotient) test -- sure, it would probably have endurance and agility and speed and power and strength measures... but could it tell you whether Lance Armstrong is a better athlete than Nadia Comaneci? Is the question even a meaningful one? And would knowing the answer tell you anything about what either one needed to continue to develop as a an athlete?
Last edited by Aimee Yermish; 08/15/10 09:07 PM.
