From the course: Cert Prep: PMI Agile Certified Practitioner (PMI-ACP)®

Sizing and estimation techniques

From the course: Cert Prep: PMI Agile Certified Practitioner (PMI-ACP)®

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Sizing and estimation techniques

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- Generally speaking, people aren't very good at making absolute estimations. It's really hard to estimate accurately exactly how long something will take to get done. In traditional project management, we knew this, so we cushioned our estimates by hours, days, or weeks in the hope that we'd be somewhat close. Agile addresses this fundamental human behavior by acknowledging that while people stink at absolute estimation, we're really good at comparing things to each other. This is known as relative estimation. Agile teams rely on this type of relative sizing to be faster and more accurate what their estimates. As an example, a soccer ball is roughly three times bigger than a cricket ball. Story points are the most commonly used measurement. They're based on the Fibonacci sequence of numbers, or some variation of it. This sequence is a naturally occurring numerical pattern that accurately reflects how things grow. It's really a simple math process. The next number is the addition of the two previous numbers, so the sequence is one, two, three, five, eight, 13, and so on. Using this sequence and knowing the pattern, we can start comparing things. If a golf ball is one, then I'd say a cricket ball is a two. What about a soccer ball? Well, since it's about three times bigger than a baseball, I'd say it's an eight. Relative sizing is the foundation of all estimation techniques used in Agile. Other techniques can be used just as successfully, so let's look at a couple. First, let's talk about affinity estimation. This technique involves grouping your stories into similar categories or affinities. There are many ways to do this, but the technique is very simple. At one end of the whiteboard or wall you'll place all your stories with a size of one, next to them the twos, then the threes, and so forth. As you continue to estimate the stories, they'll be placed on the wall in the right size affinity. As you add stories, you're comparing them to the ones already there. Does it fit? Does it seem bigger or smaller than the stories already there? If something doesn't seem to fit, the team will hold a discussion to make changes. In this way, we get a reality check to make sure our estimates are consistent. Another technique that can be used is known as Wideband Delphi. This is a group-based estimation technique where a panel of experts, your team, anonymously submit their estimates. The reason this is so valuable is that it avoids human biases. The common biases we're trying to avoid are the bandwagon effect, where people tend to go along with whichever opinion is gaining the most ground. There's also HPPO decision making. HPPO stands for highest paid person's opinion, and, as you can guess, people tend to defer to them as being experts as well as superiors. And group think, where people make decisions to keep harmony instead of voicing their true opinions. These behaviors will skew the accuracy of the estimates and impede the progress of the team. Few teams actually use Wideband Delphi for their estimates. Most teams use one of its related techniques. That technique is planning poker. It's the most commonly used Agile estimation technique. Check out this course for an in-depth explanation of planning poker. All of these techniques are designed to help teams produce fast, easy, accurate estimates for their work. Because they're simple to use and easy to adopt, you can use these techniques to help your team improve their accuracy too.

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