Monday, February 2, 2009

Uncertain of Your Uncertainty

When I was younger my family went to Versailles; this was 15 years ago or so. I remember that we were walking up the path to the entrance and there were trees overarching the pathway and a little moat on either side. The little moat was solid green and my brother and I just knew that it was painted concrete. Then my brother threw a rock onto the concrete moat, and it sank. That concrete moat was algae on top of water.


On a mostly unrelated note, I was writing about the classification of risk and of scheduling based on that. And Jeroen wrote in to ask what we do when we don't know what we don't know. This got connected to Versailles in my head (wacky, I know!). Here's the thing: my brother and I sure thought we knew something, and we were completely wrong.

We didn't know what we didn't know.

Okay, finally back to the software!

It's all well and good to give high-risk items more time and low risk items pretty close to the estimate. But when you don't know the risk, that gets a lot harder to do. And when you think you know the risk but you're wrong, you're basically in the same boat. So what do we do then?

I don't really think there's any magic here. You cannot give a good estimate until you know how much you don't know. So you start working on reducing your unknowns and avoid giving an estimate. Do the work, and make sure you promise to "give an estimate on X date" rather than guessing on an estimate early on.

Does anyone else have ideas?


  1. The Montgomery Factor:

    KIRK: Mr. Scott. Have you always multiplied your repair estimates by a factor of four?
    SCOTTY: Certainly, sir. How else can I keep my reputation as a miracle worker?

    In all seriousness, all we can do for the unknown is to make what allowances we can for them without jeopardizing our time to market.

  2. Hello Catherine,
    You triggered me to think about this. I did a short search on the internet about unknown unknowns and found and interesting classification from Roger Nunn: The "Unknown Unknowns" of Plain English. This made me play a bit with the idea.

    I wrote my idea on my own blog:

    Classification of the "Unknown Unknowns"

    As everyone already could tell me: those things are hard to schedule. I still think it is better to reserve some time for this than ignoring the unknown unknowns. By ignoring the other figures will become less reliable.

    With regards and thanks for continuing writing. I like the tone of voice you have on your blog.