I don't know that the second set of data increases the actual percentile, but rather verifies that the first was not an overestimate. Not all kids that test 145+ on one, are truly that high. Testing in that range is only so accurate. The more scores in that area, the more likely that's really where the kid falls.
Quite possibly true. I've never really thought of either of my kids as quite that high and it is possible that my younger one's one WISC-IV GAI in that range was an overestimate. She's just so wildly erratic that I also feel like the 2e end of things plays into not knowing as well. I'd suspect that there are 2e kids out there who are more capable than they'll ever show on achievement tests who don't cross the DYS threshold not b/c their IQs were overestimated, though, but b/c they have road blocks that prevent them from achieving in line with their ability. That's some of what 2e is, no?
