I am also confused about how to know when to use which version. In taking the post-test quiz for Lesson 6, Question 8 gives both the triangular and Beta answers as options. I went with triangular because it didn't indicate to me that a weighted average was required. Am I supposed to assume, as someone said before, that because there is a "policy" and previous observations regarding the time required, that a beta distribution is more appropriate? Would a triangular distribution only be appropriate if the question basically said, "we've never done this before and are taking a wild stab in the dark?"