Despite my best efforts to squash it, a rumor persists that story points are a measure of complexity. That rumor is downright wrong. The truth is, the complexity of a user story is unimportant, except to the extent that complexity affects the degree of effort required to complete it.
Let me give you an example. Suppose you and I look at a building a certain distance away. You think it’s a 5-minute walk. I think it’s a 10-minute walk because I’m on crutches at the time we have this discussion.
You and I cannot agree. You are right that it is 5 minutes (for you) and I am right that it is 10 minutes (for me). In minutes, hours, days, etc. the problem is intractable: you and I cannot agree on an estimate because we produce at different rates. â€¨
We can, however, agree that the building is “1 unit of time away.” You’re thinking 5 minutes and I’m thinking 10 minutes when we agree to that estimate of 1 unit—but that doesn’t matter. We’ve found an estimate we can agree on.
Suppose, you then point to another building and say, “That building is twice as far. It’s a two.” You are thinking it’s a 10-minute walk and I’m thinking it’ll take 20 minutes on my crutches – but we both agree it’s about twice as far.
We can agree on an estimate of 2, even though we produce (walk) at different rates. That’s what story points are about.
How would this work if we were only estimating complexity? Walking to the first building or the second building is equally complex. We’d estimate the complexity of walking to either building with the same value—let’s say a 1. What in the world would the benefit of that be? None, right? Complexity is not directly what we estimate—we estimate how long something will take and complexity can influence that estimate.
To continue our example, suppose we point to a third building. It’s physically the same distance as the first building (which was a 1). So we might want to call it a 1 as well.
Except to get to the third building we have to walk on a very narrow path over a nasty plunge into hot lava below us—the path is perhaps a foot wide or whatever you think of as narrow but traversable.
I think we can agree that walking to that building is more complex because even though it is physically the same distance away as the first, it will require more concentration and balance to walk there. We will each walk more slowly to that building—so we might estimate that effort as a 3 or a 4—because we think it will take 3 times or 4 times as long to walk to that building as it would the first building.
We are still estimating effort—complexity is a part of that discussion, but is not the thing we are estimating.
If we were only estimating complexity, I have no idea what number I’d put on that narrow walk. I really don’t—how does one estimate complexity? The only way I can quantify complexity is as it affects something else.
In the case of story points, we estimate the effort (time) to do a thing—that effort can be affected by risk, uncertainty, or complexity. So let me say it as clearly as I can: story points are an estimate of effort, not complexity.
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