Originally Posted by Alawen
[You must be logged in to view images. Log in or Register.]
I'm going to start with the very basics of psychometrics, so my apologies if this is review. I mentioned the elements of standardization, validity, and reliability in a previous post.
In brief, standardization is a given test being delivered in the same way given different physical locations, test administrators, and so on. If you've taken the SAT or the ACT, you've experienced their attempts to create a very controlled environment for taking the test.
Validity is the quality of testing what you are trying to test. This is what HBB is questioning--whether IQ is a valid test of intelligence. Validity is viewed from three perspectives: content, criterion, and construct. This is why the underlying theory of intelligence is important. I think Loraen is mostly objecting to the Cattell model of generalized intelligence; he would probably be more comfortable with Gardner's theory of multiple intelligences.
Reliability is the consistency between assessments and this is what you're questioning. It also has three subcategories, which are stability (also called test-retest), alternate form, and internal consistency. Obviously, stability is the characteristic you're calling into question.
You use a coefficient of variation to measure test-retest reliability (the quotient of standard of deviation and mean). Coefficients for both Standford-Binet and the Wechsler tests are around .90, and coefficients between the two tests, which have very different histories, are approximately .85. These are not results from a single study--this is a heavily researched area.
Most people have never taken a real IQ test. They may have received an estimated IQ based on a standardized achievement test, or taken some hokey short form internet test, but these approaches fail at all of the above. All of the standardized IQ tests require a skilled tester and quite a bit of time. As a result, they're expensive. As an aside, the popular Jung-based Myers-Briggs assessment fails horribly at reliability. Of the four elements, the only consistent measurement comes from the introvert/extrovert axis.
Returning to your question for explanations of the variance that does exist, it probably makes the most sense to consider Cattell's model. Up to this point, I've done very little speculation. This part is mostly my own thoughts. It seems unlikely that fluid reasoning (Gf) is subject to much variation. It doesn't seem to me that people learn things like curiosity and creativity. They seem to have them from a young age or not. However, it is the expressed purpose of a liberal arts education to teach logic, rhetoric, and critical analysis. Perhaps there is evidence of fluctuation in Gf between high school seniors and those same students graduating from a four-year liberal arts curriculum.
Within the limits of the model, then, variation in intelligence would most likely come from crystallized intelligence, Gc. It makes perfect sense that skills, knowledge, and experience could expand or contract with continued learning or disuse. Some of that will almost completely atrophy given a decade or two of neglect. On the other hand, some people are always learning. I like to think of myself in that group, though my skills in higher math are abominable now. I have to look up almost everything beyond simple trigonometry.
In brief, variance in test-retest reliability for standardized IQ tests is pretty acceptable, depending on what you're looking for. I think there's a lot of confusion from the simple fact that most people have never taken a real IQ test.
|
07-05-2013, 03:32 PM
Threaded Mode