Dear planners.
I like to know your opinion about the calcutation of Perfomance Factor wich is the relationship between earned units and actual units. Someones use period units to calculate that, but others use accumulate units. I mean, in some cases PF is taken as a relationship of earned and actual units from the last period (i.e. last week, las month). In others cases PF is taken as a relationship of accumulative values, earned and actual.
I think the calculation of PF using accumative units is the better option. First, this represents the total performance of the project. Second, PF with period data has more variation than accumulative data, so it is dificult to forecast the future PF.
The question is, what is the critery to calculate a well representative value of PF in order to have a good index of project's performance?