Software development which is a repeatable and already defined process is totally possible to predict and estimate. Most tasks of repeatable processes follow no

Software development which is a repeatable and already defined process is totally possible to predict and estimate. Most tasks of repeatable processes follow normal distribution and is predictable. Deviations from expected mean will be due to predictable factors of the environment such as failed disk or sleepy programmer. You can apply arbitrary six sigma methodology to measure such process with accuracy. The problem in software though is that such a repeatable process would be immediately automated away by writing a function, library, framework or any such tools that programmers use on a daily basis without much thinking. Unlike in building construction, to which programming discipline is often wrongly likened to, where construction companies simply cannot "write a function" to deploy cookie cutter houses or bridges one after another. Therefore software engineering is never a repeatable process, unless crappy tools are used, which don't allow for sufficient abstraction of repeatable parts. Tasks in software disciplines therefore don't follow a normal distribution. They follow exponential distribution most often. Most issues go unnoticed. Majority are just so tiny and ofthen considered business as usual. Every time you get stuck and have to look up a solution in docs or stackoverflow technically is an issue, but never gets reported in an issue tracker for its triviality. There are however issues which are orders of magnitude larger than what management expects when they occassionally sampling issue trackers. Some issues lead to critical design flaws which could need a full blown rewrite for example, or ever lasting and expensive hackery in case the executive decision is to work around the critical design flaw. These issues can take years to accomplish or take massive amount of pain endurance. Trying to estimate a process with such exponential distribution and making sense of averages or other statistics of such distribution is borderline insanity. Why not just go to physics department and ask when the next Theory of Relativity will be invented and how much budget and story points those guys need.