Why Manual Estimates Are So Bad
It took me a long time to figure out why most people do such a poor job estimating effort and schedule manually. Some of the top reasons include:
People Estimate the Go Path:People Aren’t Too Bad At Figuring Out What It Takes To make the system do what it should. They usually miss terribly in estimating what it takes to make sure the product doesn’t do what it shouldn’t. In software, for example that would be dealing with bad inputs, hardware issues, etc.
Technical Pride Forces Root Level Activities Take Longer:Even when tasks are well understood and estimated at the root level, personal pride causes projects to talk longer… As people provide estimates at a very high probability (experienced people don’t want to be shown to have overrun… if they do they lose credibility… And if they under-run they also lose credibility. So they must estimate at a high probability then do other good things (gold plating, additional testing, etc.) when the task comes in under that high estimate.
Their Estimates Are Cut In Half Or Tripled So They Try To Outsmart Management:Some organizational cultures include management cutting the estimates without cutting the work. Wise developers know this and increase their estimates so when cut they can still succeed. Talk about dysfunctional!
People Don’t Document What they Are Estimating and Validate Assumptions: I lost count decades ago of the number of estimates where people really don’t even clarify what they are estimating. I understand systems change and estimates may need to change but these people don’t worry about details like what functionality is included or excluded in this estimate.
I could go on and on but these are some of the basics. Feel free to add your list in the comments.
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