Disclaimer: I will not go into the story points (SPs) pros/cons battle. If you use SPs (or T-shirt sizes) you might find this technique useful. If you don’t then this post is probably of no value to you.
I know some teams that plan their sprint based on the number of story points (SPs) that they finished in the previous sprint(s). So if they finished 30, 27, 32, and 31 SPs in the previous sprints they will consider everything close to 30 a reasonable number but they would reject the idea of taking 40 SPs. And rightly so.
I believe this is not enough, at least not enough if your stories vary in size. I mean, if all your stories are estimated to 1 point, then I guess such a sprint capacity planning is all you need. But if not – and in the majority of cases that I’m aware of it is not – then you need something more.
1+1 != 2
Why? Because story points don’t sum up so easily. Closing a story estimated to 5 is not the same as closing five stories each estimated to 1. First of all, because in general SP is a pretty rough estimate. Second, because it might take a different way of working to be proficient at dealing with 5s than at dealing with 1s. Writing five short stories is not equal to writing a novel.
So, what could we do about it? Ah, there is a simple technique that could help you. So basically, you should remember not only the number of story points delivered in the previous sprints, but also the distribution of stories, like this:
So now you know much more. As we can see there is a mixture of stories of different sizes which the team is able to deliver during a sprint. For example, we can see that during one sprint the team never finished a story of 13 SPs and never delivered more than two stories of 8 SPs. Which makes you cautious to agree with committing to a sprint of 2 stories of 13SP and 1 of 5 SP, even if it sums up to a “reasonable” number of 31 SPs.
TIP: Of course, you could (and probably should) add some more info to this simple spreadsheet, i.e. keep track of ppl availability so that you know how absence affects team’s ability to deliver.
That is it, have a nice day!
P.S. Size of stories
Long story short, there are two most widely used measures of story sizes.
First, there are the numbers from Fibonacci sequence:
Second, you could use T-Shirt sizes, using 3 (S, M, L) or more sizes, e.g.: