But there is no correct time. That's a deterministic paradigm, whereas tasks are probabilistic events, with a distribution of possible points. Take a given task, and there are versions or scenarios where it takes 1x units of time, all the way to 100x. What critical chain does is help the worker play with the 3 sides of the PM triangle, time, budget, and scope, in a way that optimizes for the global throughput, not just their little local optimum.