Planning fallacy: why people suck at planning and what to do about it

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13 pointsalinavrabie5 comments

Terminology nitpick: this article is not about planning, it's about estimation.

Estimates, plans and commitments are three different things (see http://www.amazon.com/Software-Estimation-Demystifying-Pract..., which is the best book I've read on the subject).

The problem with estimation in many cases is that people who dictate requirements often dictate commitments as well, and do so without estimation-based feedback. In other words: "Your ten-week 'estimate' isn't acceptable; we have to have this done in seven!"

In this example I would say commitments are getting in the way rather than the estimates, and the overall plan gets messed up.

The way I see it, good estimates are simply a prerequisite to good planning, so they tie in together.

Another interesting division, from Software Estimation by McConnell is Estimates vs Targets vs Commitments. You could add "Goals" and "Plans" to that perhaps.

The interesting insight here for me is that my tendency to under predict task times is ego driven. I always thought it was optimism ;-)

I guess our ego does a good job at fooling us :)

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