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> you need to do some more maths with the three numbers to figure out what the right date to use is. We did this all the time at a previous job. We had a spre
by drdec 5y ago
> you need to do some more maths with the three numbers to figure out what the right date to use is.
We did this all the time at a previous job. We had a spreadsheet in which we put in the three estimates. They were combined in some ratio (I think it was 1 part each for the outliers and 2 parts for the most likely). Then some time was added on for testing, test remediation and project management at a set additional percentage. Worked out pretty well, we seldom ended up with issues when using this method.
- regularfry 5y agoTom DeMarco describes a method in Waltzing With Bears that's quite interesting: use a triangle defined by the three points as a rough approximation for the probability distribution, and then cumulative distribution function calculations are just juggling quadratics that you can plug into Excel. Mind you, these days Excel's got the distribution function formulae in it that you'd need to do it "properly" with a lognormal distribution, but I like the way the three estimation points have a direct and obvious link to the result with the triangle method.