Hour-glasses and empirical process control: a good metaphor

hour-glassOne night I was paying my bills, and suddenly I saw a tiny hour-glass on my desk. My wife probably left it there for some reason… But after I saw it, I wanted to know how much time it would take to pass all the sand from one side to the other. Curious as I am, I turned it and started to count. After a few seconds, like a flash, I stopped it, putting it with the two sides on the desk, because I saw Scrum happening right in front of my eyes, clearly as water, and in a sufficiently easy way to explain it to anyone else! Actually, I saw not only Scrum, but any empirical process control method.

What happened? I didn’t know how much time it would take to pass all the sand from one side to the other. This situation is like an unestimated product backlog: you just don’t know how much time it will take to build it. So, I made a guess: 5 minutes. Then, after 30 seconds, I stopped the hour-glass, looked how much sand passed, and made a new guess, given the amount of sand and time passed. This was my first sprint! After 3 sprints, that is, one and a half minute, half of the sand had already passed. So, my guess to the total time needed was certainly 3 minutes, and that was right! With only half of the sand in the other side, I had the exact amount of time that the hour-glass needs to pass all the sand from one side to the other! WOW!

That’s it! Empirical process control for dummies! =)

7 Responses to “Hour-glasses and empirical process control: a good metaphor”

  1. Explaining empirical process control to a product owner « Agile Inquirer Says:

    […] Agile Inquirer Questionings and discoverings about agile software development « Hour-glasses and empirical process control: a good metaphor […]

  2. Explaining the value of estimation to the team « Agile Inquirer Says:

    […] Before the next release planning of Brasigo and BlogBlogs, I called each team to show them the hour-glass metaphor. The message I wanted them to understand was: estimation gives us predictability, and this is […]

  3. Jacob Karma Says:

    Beautiful 🙂

    But if you’d taken the time to really examine the hourglass, you’d have been able to give an accurate estimate before having to watch the sand flow at all…

  4. Antonio Carlos Zegunis Filho (tucaz) Says:

    Hmm! Very nice and simple explanation about agile estimating!


  5. caike Says:

    Very nice! I´m also a fond of comparisons and find myself doing them all the time.

    However, I think your comparison is an analogy rather than a metaphor.

  6. alandd Says:

    Very nice and simple! Excellent observation. Thanks for writing it up, I’ll need to use if very soon as our company continues adopting more agile practices.

  7. Richard Says:

    That’s all very well, if all the grains of sand are the same size. Unfortunately, in a poorly made hourglass, as in a badly defined project (or even a well defined project in an unfamiliar domain), the sand may not be all the same size, and may flow at uneven rates. Indeed, if it’s a really cheap one, you might get a cluster of sand that does not go through the hole and gets stuck, until you give the hourglass a jog! Sound familiar?

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