Okay, thanks. The only thing I had right off the bat was CMP%, that one is obvious. I'll go back and look again with my new-found knowledge. Who decides what each of those things are besides for CMP%? The rest seem pretty subjective.
For xCMP%? It's a standardized metric based on historical data, using variables like down, distance, receiver separation, ball placement, time remaining, whether they are outside or in a dome, etc., to determine the probability of a completion.
I suppose you could say there is mathematical subjectivity in how the model is built, but in a general sense it's not subjective. In fact, the calculation and application of xCMP% are fundamentally objective. It's not like PFF where someone is grading each play. That's true for every stat in that picture.