Hm, a stats munchkin.

Well, I'd as say the approach factoring vs. sieving is quite different, there should be a seperate statistic.
I don't know the effort-relating factors (pun not intended) for the factoring, but they are different from those of sieving. So the effort estimation shouldn't be done on the basis of the factors.

Ok, that's basically the same as Moo said... <-- *selfslap*

Well, I thing this is something to be discussed on the way, but it should be no obstacle for factoring.
At least as long as it doesn't stop me from climbing the stats ladder.