Wednesday, June 5, 2013

Is your fuel gauge agile?

It seems that there is always confusion the first time someone rolls up on an agile methods burn down chart:
  • What are we burning?
  • How much is there to burn?
  • How long does it take?
  • What is the starting point?
  • When does it end?

An analogy
Think of a burn down chart in the same way you regard the fuel gauge in your car:
  • You fill up the tank
  • You drive around, consuming fuel
  • Eventually, it the fuel runs out, the gauge shows empty, and the car stops
So, to make the analogy:
  • The gauge, if it has any metric calibration at all, probably says "full" at the top.
  • Let's say that "full" is 20gal (US) or about 75ltr. So, the gauge could read 20gal instead of "full".
  • But, if the car gets 30mi/gal, then the gauge could read 600mi (965km) when "full" instead of 20gal. Some driver digital display systems give such measures
  • But, if you drive about 10mi (round trip) every time you run an errand, go shopping, go to a restaurant, etc, then the gauge could read 60 trips when "full" instead of miles or gallons. Naturally, when the gauge gets to 1/2, then you've got 30 trips left in the tank.
And so it is with a burn down chart.
  • Typically, we're burning some consumable resource, like hours (gallons of fuel), to empty the backlog (tank)
  • When the backlog runs out, we stop
  • But, we could look at some velocity, a rate of consumption, like stories per hour (miles per gallon)
  • Or, we could look at the number of stories (trips to the store) we expect to complete if we burn all the hours (fuel)

Check out these books I've written in the library at Square Peg Consulting