Story Points – what’s with the missing numbers?
First let's talk about Numbers, then something else, and then Story Points.
Number, integers and real numbers provide the scientist with a very valuable tool, a continuum of regular spaced labels for comparison purposes. These integers are sequential with no gaps or voids. This is quite special in nature, for there are very few things in the natural world that are so regular and consistent over an infinite range.
Let's look at the number 10. It's a nice round number (divisible by two) and it has a roundness to it's drawing. It is a commonly used end point in quizzes and surveys. Is there something special about it - why not use 12? Chicken farmers do, bakers do, why don't we in the Agile software world? No - we use unlucky 13.
What's your favorite font size? I'm betting 12 point. Because it is the default on most software programs - I'll wait take a look. While you're up there at the font menu where is font size 13? Maybe right there below 12. Where is size 15? On one of my favorite tools the drop down goes 8, 9, 10, 11, 12, 13 14, 18, 24 ....
What's wrong with 15 point? And why are all those other numbers missing?
While we're talking fonts, I remember back in the early 1990s teaching people about fonts, font styles, and font sizes. Back then we had more choice. One typically entered font size in a free form text box, you could have any size you thought might be pre-loaded on your computer. Fonts were static in size and not scalable (TrueType). There was a lot to learn about fonts. What's a point? Well it turns out I know what a point is: and 72 of them can dance on a ruler within the tick marks of any inch.
Story Points the missing numbers
Agilist typically use a range of numbers with gaps to describe XP User Stories effort estimates (size). One common set of numbers is the Fibonacci Sequence, or a modified Fib-Sequence (fib as in lie).
1, 2, 3, 5, 8, 13, 21, 34, 55, 89, ... (Fibonacci Sequence)
1, 2, 3, 5, 8, 13, 20, 40, 100, 200, ... (the Fib-Sequence)
Mind the Gap please. Well are you OK with not finding the 15 pt Font Size? Then why do you get so concerned about a few missing story point sizes. It's the same damn thing. Nobody wants to use font size 34 or cares about the difference between the 12 point story and the 11 point story - just call them all 13 points and move right along, nothing to see here folks.
measurement system of teaspoons to cups (48 = 1), or pints, quarts, gallons (8=4=1). Or teaspoons, tablespoon, cups, pints, quarts, gallons ( 768=256=16=8=4=1).
One reason is the utter simplicity of the Fibonacci sequence and that it is an additive system of relative measures. The sequence is granular at one end and smooth at the other.
If the opposite of granular is smooth, then which end of the Fibonacci Sequence is smooth and which granular? Why does granular have a small connotation? I think this is why I don't like the word granular - it's ambiguous when typically used.
Let's recap - in the 1970s it was the metric system, in the 1990s it was the Font Size, and now in the 2010s it's Story Points.