Deriving Project Estimates

Normally estimates are derived with a 50- 50 confidence.  But  is a fifty-fifty case okay while setting  your goals/targets/specification limits ? People will prefer to have a better confidence while setting their goals. So what should be done.? Some improvements needs to be brought in to the current system . Those improvements needs to be chosen in such a way that it will have a positive impact on the goals.

Now, consider a project scenario. Project A sets their effort estimates as 100 Person Days (PD).  This needs to be submitted to customer. In order to deduce this they took the below steps Step 1: Baseline the organizational productivity (LOC/PD), found 10 LOC/PD as the central value Step 2: Estimate the size of the project, found as 1000 LOC Step3: Convert the size to effort using productivity baseline, found to be 100 PD. And this is submitted to customer. This project team is aiming 20 % an improvement in productivity , i.e. 12 LOC/PD. From this statement, infect it is not clear whether they are aiming to achieve a productivity greater than 12 LOC/PD  with a 50% probability of success or with a greater probability. Now let them redefine the goal statement as ‘greater than 12 LOC/PD  with at least 80% probability of success’.  So this implies that the project team needs to have  improvement initiatives to make the increase in productivity with required probability of success . ……

With this, it is clear that the possible central value of the redefined specification limits must be  above to 12 LOC/PD. Using the normal distribution function, it  is seen that if central value of redefined goal is near to 13  ( assume standard deviation of 1), the probability of success would be greater than 80 %. In that scenario project team needs to deduce the internal effort estimates with current mean, i.e. 13 LOC/PD. Then the effort estimates becomes 77 days approximately. So this internal estimate shall be used for further resource planning and assignments within the project team.


Akhila is the founder and sole contributor of and By profession she is a software Quality and Quantitative data analyst. She is a self motivated life long learner who loves to decode signs from the universe. Her weirdness is totally aligned with her real life stories and thought experiments. She is the author of “Know them, One answer to many questions” (a General Knowledge book) and “I Had a Crush - The 17 Kinks” (A free ebook of 17 short stories)

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