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Lauri Hiltunen
Lauri Hiltunen

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Estimates and Anchoring When Playing Planning Poker

Rudimentary Introduction to Planning Poker

The term of planning poker is used to describe the method which utilises a group of developers to estimate the relative size of a development task, or multiple of. When a team is playing planning poker, people go through the tasks one by one, estimating the task as they go. You can read more about the method in Wikipedia, for instance.

One benefit of planning poker is including the opinion of each developer when the estimates are done. Generally the more experienced developers, who might know the system inside and out, may lean on the smaller side of the estimate spectrum. This is quite natural, as it is how that person sees the task. What he might fail to note is that not every developer in the team shares the same experience, expertise or insight on how the app works currently.

Before Moving on...

Before we move on to the cool stuff, try answering these two questions. I promise it'll make sense in just a minute.

The Cool Stuff

Now, where the game gets interesting is the psychology behind it. The Wikipedia description includes this, sometimes overlooked rule of planning poker: "all participants show their [estimate] card at the same time". For a successful round of planning poker, I consider this quite essential part of the game. Why, you might ask...

It all boils down to something called the anchoring effect. In a nutshell, anchoring means using some initial piece of information as a base on which we build our own opinion of the matter. Daniel Kahneman's Thinking Fast and Slow elaborates this by using an example:

The guests at San Fransisco Exploratium were subjected to an experiment to see how the anchoring affects people's estimates. People were split into two groups, each of which two questions were asked as follows:

Group 1
Is the height of the tallest redwood tree more or less than 365 meters?
What is your best guess about the height of the tallest redwood tree?

Group 2
Is the height of the tallest redwood tree more or less than 55 meters?
What is your best guess about the height of the tallest redwood tree?

What was noted that the first question affects how people will respond to the second question. The average estimate of height of the tallest red wood tree for the group one was ~257 meters while the group 2's average was around 85 meters. Quite a big difference just by changing one number in the first question. The anchor.

So if we skip the "everyone reveals their estimate at the same time" we establish the possibility to anchoring to happen. It means that whoever speaks their mind first might affect the estimates of people coming after them. Following estimates might not necessarily become the same, but it's easier for the person to drop their original estimate of 5-7 points to 3, for instance. And that's a big difference.

The lesson is this: if you're playing planning poker, go all in!

P.S. Oh btw, about the answer you gave earlier, did your answer reflect with the findings described above?

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