Probability of Success for a Project

I have been thinking about something lately: How does a project manager know at any point of time in his project, what is the probability of success for his project? There is definitely a need for such a tool which will help the project manager quantify where the project is headed. This would help him in taking corrective and preventive actions in various areas so as to bring the project in track. As of now, there are various metrics collected for a project. The metrics collected differ in different stages of the project. But if you ask for a single figure which will gauge the probability of success, I am not aware if there is anything which can help. Presently, I would say that most of the project managers go by whatever discrete metrics which are collected and their individual gut feel to assess the pulse of the project.

The more I think about this, the more I am convinced of the need for such a tool. For example, during the initiation of a project, there are certain parameters that should be measured. Similarly, during the requirements stage, certain other parameters needs to be measured. Similarly during the design, development, testing and implementation phases, other parameters are measured. All these parameters should be combined in a way to give us the success measure of the project.

The risk metrics may be the one that represents the probability of success of a project closest. Somehow if the risk metrics can be combined with the review effectiveness at each stage, the defect leakage for each stage and the cost/effort and schedule variance, along with a parameter to quantify the trace-ability, and may be many other metrics, we may be able to come up with a general dashboard which can give us the pulse of the project. It should factor in any dependencies between various parties involved in the project.

Some of the things mentioned above are reported in status reports. But as someone had stated, Status reports are rear-view mirrors. They show what has already happened. It may sometime give us a leading indicator of the success or failure of the project. The Traffic Light reports with Green, Amber and Red colors tell us where the project is headed. But again, it is very subjective and not quantifiable.