studying the details of PERT/CPM, I'm perplexed when I read the formula of duration of an activity is
expected time = (opt. time + 4medium + pess. time) ÷ 6
because it's following a Beta distribution.
I don't understand the cause. The Beta distribution is an extension, in continuous mathematics, of a Bernoulli distribution. This means that, in this distribution:
- every event is independent by the previous and the next;
- that are only 2 possible values, yes/no or similar;
I don't understand how to link these properties with the estimation of activities in a project.
Can you explain to me, please?