PERT project estimator

The math is the standard PERT set: each task gets E = (O + 4M + P) / 6 and SD = (P - O) / 6, project expected time is the sum, and the project SD assumes tasks are independent, which real projects are not: shared people, a slipped dependency, or one underestimated integration correlates them, so the true spread is usually wider than this range. Deadline probabilities and the commit date treat the total as normal, which is the central limit theorem's comfort, not a guarantee; a project with one dominant task keeps that task's shape. Zero-spread projects (O = M = P everywhere) get a straight in-or-out answer instead of a probability.