Those of us that can do the maths. The relivant caculation is:
Ew=A*meanAE
AQ=AE
So
MeanAQ=Ew/A
Where
A= no of articles E=effort w=wikipedia Q=quality.
I don't remember ever learning that one in my math class.
Let me expand on why that equation is bullshit. Effort is not a constant, and the more articles you have, the more contributors you'll have, and the more effort you'll have. Also, not all effort is equal, nor does it have an equal effect on quality. In fact, some of the worst quality articles happen to be the articles which have the most editors, and the most effort, spent on them. Keeping around a short factual article about an obscure topic is not going to bring the average quality of the encyclopedia down. In fact, a short article on an obscure topic is easy to make into a high quality short article on an obscure topic, and will therefore bring the average quality of the encyclopedia up.