We estimated 300 development hours, but when discussed with management, they think we overestimated. How can we keep them out of our development process?I'm sure you, as a programmer, are familiar with the sting of anger felt when someone "corrects" your estimates.
What's the feeling? Anger, frustration, humiliation? Probably a little bit of all.
It comes from the fact that they are not trusting your work as a professional.
It's important to realize they aren't doing this because of spite. They simply don't understand development and the complexity of it.
Or for that matter, it may be that they have bad experiences with some programmers or have been taught to distrust estimates in general. Either way, the result is a nasty conflict.
The solution is not to keep them out.
Input from stakeholders is crucial for a successful project! The problem is when they are overstepping boundaries. The way to handle it is to agree on a contract consisting of two simple rules:
§ 1 Developers should have the right to estimate their own work.
§ 2 Stakeholders should have the right to prioritize among that work.
So instead of wasting time arguing, just agree upon this, respect that both parties will do their work and let the forces of collaboration do its thing.