How many times have you given an estimate only to have the business partner try and negotiate you down? In my own recollection, pretty much every time I’ve ever submitted an estimate there’s more push back. Now, that’s not to say my estimates are any better than anyone else’s or that my teams are more efficient. These were questions, at the time, that I didn’t think enough about to collect the data to answer.
But, the estimated cost of a project came up today. It was a huge project we were discussing, perhaps several million dollars in total spend. At some point the conversation turned to a small piece of the estimate. It was just ten thousand dollars or so, but we were discussing if it was the right number. Think about it… In the scheme of several million dollars, what’s ten thousand? It’s less than likely error in the estimate, that’s for sure.
Which is the point of my post. At what point do you know that the proposed reduction in the estimate is meaningful? If you do a point estimate, you probably don’t have any frame of reference. If you provide a best, likely and worst case estimate, however, you can begin imagining how you’d figure that out. If the changes made don’t bring the likely cost below the best case cost, you’re probably arguing about estimating error and not a meaningful difference in the scope or scale of the work.
From folks like Steve McConnell we know that developers are chronic under-estimators. Why then would you allow yourself to be pushed into an even smaller estimate, particularly when you know you were likely to come out worse than your likely case estimate anyway? If you’re going to revise your estimate downwards, make sure it’s for a meaningful change in the scope of the work, not just optimism or bullying on the part of the business. In the long run, you’re doing them no favors by caving in when you can’t reasonably deliver whatever it is for that cost. Now, figuring out how to be more efficient, that’s an entirely different topic.