I am very often in an environment where the employees performing the work are constantly rolling over to new employees and these employees are allowed to estimate on their own how long tasks will take. I have found that the error in their estimates always seems to be the same. Like if Bob over estimates on task 1, he is very likely to over estimate on task 2 as well. Same thing if Jim under estimates on 1 he will probably under estimate on task 2 as well.
So my question, is there any way to perform a quick test of sorts to identify these trends before starting into actual work? This post seemed to hit some of my questions, and I like the PERT method as described by Bill the Lizard. Ideally what I would like is to be able to very quickly identify if I need to change the weights of Optimistic, Expected, and Pessimistic for that person in order to better estimate how long it will take.
Since there is such a fast roll over it seems like about the time the employee has done enough estimates/work to know how to treat their estimates they end up moving on. So, any suggestions on how to handle this? Would going with something other then PERT work better?
And PS, the fast roll over is due to it being a student driven group so it is expected that the student will leave once they graduate.