Hello:
We have received a request to provide time estimate (and cost estimate) for a big IT project that involves complex migration from legacy system to current technology.
We have used simple task break down structure in the past for small projects and found them to be reasonably acceptable. Are there any tools or best practices for estimating time/duration of a complex project?
When it comes to estimating, my favorite tool is using PERT. You take three seperate estimates - pessimistic, optimistic and most likely and then divide by 6. The formula is as follows: O + (4*M) + P divide by 6. Most project managers remember and use effort and availability but something that a lot of people forget about when they are estimating is productivity. Not all people have the same productivity rating. The average according to studies is 75. Someone who is more senior may be a bit more productive while someone junior may be a bit less. The formulat you would use for duration would be as follows: duration = (effort\productivity) \ availability
I've also attached a little table that I learned in one my classes about etimates that I find helpful when explaining to project sponsors as to precision of the estimates and consequential schedule. Saving Changes...
