Those of you who’ve been working in the IT world may have noticed that your projects rarely get done on time. This blog entry is about dealing with the ‘overly optimistic’ estimates your IT staff normally produces. Here’s a technique you can use to counter the overly optimistic developer.
As I noted in the previous blog entry, there are two types of estimates; order of magnitude and definitive estimates, with definitive having two sub-types (duration and work effort). You already know you need both types of definitive estimates to make sure you’ve got valid numbers for your project. The next step to counter overly optimistic estimates is called three point estimating and deals with a further refining of the duration estimates. You’ll be getting three different ‘views’ for each duration estimate.
The first estimate you get from your developers is called a ‘best guess’. This is more than likely the number they’ll give you as their first estimate. The second estimate you’re going to ask them for is the optimistic estimate – how long would it take if everything went perfectly. The third estimate you’ll ask for is the pessimistic estimate. For a pessimistic estimate, you try to account for everything that could go wrong and factor that into the estimate.
After you’ve gotten the three estimates, allow the developer another chance to refine any of the three numbers. Inform the developer you’re going to use their best guess estimate as the schedule for the work to be done. In reality, you will use the pessimistic estimate for building your project schedule. My experience as a project manager in IT shops, as well as those of my peers, indicates that IT developers are almost always overly optimistic about what they can get done.
I know this seems like a lot of work, but this is actually one of the simpler techniques for arriving at valid estimates. If you want to deliver your projects on time, you need to take the time to get the three estimates that make up a three point estimate.
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