And it also assumes that the optimal is just as likely as the pessimistic. As anyone who has ever planned anything knows, more things can conspire to introduce delay than work out just right enough to make it take less than you excepted.
Right, and there's lots of literature jumping on that and trying to repair it. Yet the original formula outperforms single point estimates.
But as I said elsewhere in this thread, my suspicion is that the unpacking effect dominates the "improvement" that's observed and that the particular formula is largely secondary.
