Just rankings don't tell enough of the story, though; if they measured 1000 schools all of which had excellent air, there'd still be 250 in the bottom quartile. (Or, alternatively, and perhaps more likely in the real world, if they measured 1000 schools all with poor to awful air, there'd still be 250 in the top quartile.) So the question is what does the actual curve look like? I guess I could try reading the positions of the two sliders for a little more detail; but I don't know what risk levels their "best" and "worst" mean, or what the slope of the function is.