8. There Is No Correct Estimation Model
For years, we bought the cone of uncertainty for estimation—that is, our estimates were just as likely to be over as under.
Cone of Uncertainty
Laurent Bossavit, in The Leprechauns of Software Engineering (BOS), shows us how that assumption is wrong. (It was an assumption that some people, including me, assumed was real.)
This is a Gaussian (normal) distribution. It’s what we expect. But, it’s almost never right. As Laurent says,
“Many projects stay in 90% done for a long time.”
What curve do our estimates follow if they don’t follow a Gaussian distribution?
Troy Magennis, in The Economic Impact of ...
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