2 ms·
Yes they have. You get D-K exactly when you run the simulation of the data collection with ceiling/floors, and you have to for basic statistical reasons. There'
by gwern 6y ago
Yes they have. You get D-K exactly when you run the simulation of the data collection with ceiling/floors, and you have to for basic statistical reasons. There's nothing to explain. D-K does not exist, and OP is misleading in trying to 'correctly' explain research that was wrong to begin with (he gets only halfway there when he admits that regression to the mean forces much of D-K, but then handwaves furiously that it can't explain all of it, when the other measurement problems account for the asymmetry in how much the top/bottom groups regressed).
- alisonkisk 6y ago> when the other measurement problems account for the asymmetry Such as? And what about the 2nd and and 3rd quartiles? And even if the phenomenon is caused by the mathematics of floor/ceiling effect (low skill people bias their assessment upward because they know they can't have a negative percentile), it's still real effect in misestimating their percentile. Baseball players at bar can be modelled by random numbers too. That doesn't mean variance in performance over time is purely random.