My project manager assigned me a task to estimate the development time for an iPad application. Lets assume that I gave estimation of 15 working days. He thought that the number of days where too many and client needed the changes to the application urgently (as in most of cases).
So, he told me: "I am going to assign two developer including you and as per my understandings and experience it won't take more than seven working days."
Clarifications
I was given the task of estimating development time for an individual. How could I be sure that 2 developers are going to finish it within 7 days? (I am new to team & I hardly know the others abilities)
Questions
- Why do most of project managers / team leaders have understandings like:
- If one developer requires N days,
- Then two developers would require N/2 days,
- Do they think something like
developer = s/w production machines? - Should a team member (developer, not team lead or any higher post) estimate other developers work?
I didn't deny anything in the meeting and didn't said, but what should be the appropriate answer to convince them that N/2 formula that they follow is not correct?
Best Answer
Only really experienced developers are able to estimate properly. The reason is that the repetitive comparison between his estimations and what really happened (errors) teach him intuitively to increase his abilities.
Very few experienced developers or managers are able to estimate for others. Estimating for a whole team is even more complicated, and I personally believe it's impossible without proper tools.
That's why collective estimation such as planning poker coupled to velocity tracking is the way to go.
Planning Poker helps team avoid being affected by cognitive bias (thoughts being influenced by beliefs, environment, etc), while velocity tracking, later used in planning helps the manager to convert subjective estimations to realistic estimations.