When I studied testing in graduate school, the first consideration was always: Does this test actually test what it is intended to test?

It's a contrived stat created to give stat wienies something to argue about. Baseball is a team sport so measuring the value of individual players is stupid.

Hi, Gene. Piaget's original "IQ" test was intended to attempt to predict students' potential to succeed in the French school system. Over the years, that unfortunately morphed into some silly industry to measure some magical thing without that grounding. So, yes, it's predictable validity, or it's subsidized crap. Reversed, some tests, like Wechslers, could be used to look at the effect of such educational investment, or the lack thereof. My favorite client/patient in this regard was a juvenile named Phil (hey, it's been 30 years), who just hit an 85 IQ - and could steal a car in around 60 seconds. Baseball, like most sports, is rife with descriptive statistics. A fine line of chatter, and that's about it.