Agile estimating 1/4: Ideal versus elapsed time measurement

Written by , in category Agile & Scrum

30 November 2012

Why is it that people always think they can estimate the time it will take to finish some amount of work using this wondrous concept of ideal time? Hey, I’m not saying I never do that, I’m one of those people doing just that. What do we think this ideal time consists of? I like the example of a typical NBA match. Ever watched the NBA? No, well you really should. It’s really cool and intensive. Now for those who are very familiar with the NBA, this might be a very trivial question.

How long do you estimate an NBA match takes? It depends on your point of view of course. The ideal time, used by officials to know when the game is over and when breaks are due is 4 times 12 minutes and a 15 minute half time. This is actual game time, when the clock is running. From a lean perspective we could say this is similar to the concept of Touch time. The time during which you are actively working on something and not being disturbed, having to wait or any of those things. These are things we assume when we talk about ideal time. That we only do one thing and forget about all the rest. It also presumes that we will not be disturbed and will not have to wait for anyone. We should also have done all preparations necessary to be able to start the work without further ado.

Is this time measurement really useful? Think about all the daily interruptions, ranging from phone calls to e-mail, from meetings to helping out people around you, from social media to personal issues. Not to mention the fact that we depend on several people in our team to be able to finish our work and do it effectively. Why do we need this estimate anyway? Right, to plan. So if we go back to our NBA example, what you really need to know is how long will you be hogging the tv? Because that’s what you are going to have to negotiate with your partner.

This is the elapsed time, which is typically about 2 hours. In lean vocabulary we would call this cycle time, the time from when we start something to when we really finish something. This measurement actually takes into account waiting, disturbances, context switching and preparations. So what do you think your ideal / elapsed ratio is? If 8 hours pass in a work day, what % of that time was actual ideal or touch time? I’ve asked this question to hundreds of people before and the answers mostly range from 15% to 75% and I tend to believe the people that were closer to 15% more.


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