I Ran Out Of Time! (Why Are Software Estimates So Bad?)

I read an interesting question on Quora regarding task estimation. The question, “Engineering Management: Why are software development task estimations regularly off by a factor of 2-3?“, had an answer wiki attached to it and then some quite long and specific answers. There is a lot there for anyone who works with students, and I’ll summarise some of them here that I like to talk about with my students:

  • The idea that if we plan hard enough, we can control everything: Planning gives us the illusion of control in many regards. If we are unrealistic in assessment of our own abilities or we don’t account for the unexpected, then we are almost bound for failure. Making big plans doesn’t work if we never come up with concrete milestones, allocate resources that we have and do something other than plan.
  • Poor discovery work: If you don’t look into what is actually required then you can’t achieve it. Doing any kind of task assessment without working out what you’re being asked to do, how long you have, what else you have to do and how you will know when you’re done is wasted effort.
  • Failure to assess previous projects: Learn from your successes and your failures! How much time did you allocate last time? Was it enough? No? ADD MORE TIME! How closely related are the two projects – if one is a subset of another what does this say for the time involved? Can you re-use elements from the previous project? Be critical of your previous work. What did you learn? What could you improve? What can you re-use? What do you need to never do again?
  • Big hands, little maps: There’s a great answer on the linked web page of drawing a broad line on Google maps at a high-level view and estimating the walking time for a trip. The devil is in the details! If you wave your hands in a broad way across a map it makes the task look simple. You need to get down to the appropriate level to make a good estimate – too far down, you get caught up in minutiae, too far up, you get a false impression of plain sailing.

I found it to be an interesting question with lots of informative answers and a delightful thought experiment of walking the California coast. I hope you like it too!



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