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?
Just pointing out that there are other ways to do it, too: by functional area, or subcontractor. Some studies have shown that performance factors are quite stable by type of work. So let's say that a sub has performed poorly on the project -- but 99% complete. By isolating the sub's poor performance, yet showing that that work is complete, we don't have to "staright-line" the underperformance across the future project work.
Fraternally in project management,
Steve the Bajan
I agree with Glen.
I always report both, and annotate the graph to provide commentary on reasons for large over/under performance in any given month.
If for some reason you can only report one, I would choose the whole project rather than period performance.
Alfredo
Consider using both. Cumulative will give you a view of productivity over time while period will give you a view of trends. Period trending can be invaluable in helping you identify specific events or circumstances which have or are impacting productivity.