And account for correlations. It would be interesting to see if multi step projects with overruns tend to overrun in more steps then expected. I could imagine a

And account for correlations. It would be interesting to see if multi step projects with overruns tend to overrun in more steps then expected. I could imagine a stakeholder management heavy project to be more likely to overrun in every step. In other words, even by summing the distributions you might be underestimating the expected time of completion.