What Values and Sequence to use for Story Points
Companies and team use different sequences to identify values to assign to User Stories. These values are called Story Points. Following are four most common sequences I can find
Jagmeet Singh writes about Technology and Business on W3Courses.com. Jagmeet is the owner of Parallel Exchange and developed Phonora Photo Galley software product. In his spare time he enjoys photography and loves to travel.
Agile, Scrum, Story Points, User Stories, s
Fibonacci Sequence
The Fibonacci Sequence includes the following values:
1, 2, 3, 5, 8, 13, 21, 34, 55, 89, ...
The sequence F[n] of Fibonacci numbers is defined by the recurrence relation:
F[n]=F[n-1]+F[n-2]
with seed values F[1] = 1 and F[2] = 1
By definition, the first two numbers in the Fibonacci sequence are either 1 and 1, or 0 and 1, depending on the chosen starting point of the sequence, and each subsequent number is the sum of the previous two.
While talking about why we use Fibonacci sequence with my team. I asked one of my team members to explain the difference between stories with consecutive scores like 5 and 6 or 7 and 8. I added that the fact that these values are further apart implies that we are forced to make a choice between the amount of significant effort a task will take to complete.
The human mind perceives a difference between 5 and 8 story points or 13 and 21 story points. However, human mind gets fuzzy when deciphering difference between 19 and 20 story points. In addition, it is difficult to establish a ratio between a 5 and 6 than 5 and 8 or 8 and 13. The fact that the intervals between values is increasing forces the mind to perceive a visible difference in magnitude.
Story Points themselves are relative estimates of the amount of effort involved, not a precise amount of hours required to complete a task. So, Fibonacci sequence serves as a very good scale to estimate StoryPoints for user stories.
Fibonacci-Like Sequence
Fibonacci-Like Sequence is my preferred sequenced to use for story points. I used Fibonacci-like sequence while developing the Phonora Photo Gallery software. The Fibonacci-Like Sequence is based on Fibonacci Sequence, however the numbers are rounded up or down to the nearest 10th.
The sequence includes the following values:
1, 2, 3, 5, 8, 13, 20, 40, 60, 100, ...
The first five numbers upto 13 remain the same as Fibonacci numbers. 20 replaces 21, 40 replaces 34, 60 replaces 55, and 100 replaces 89. This is because there is usually a margin of error in estimation work effort. 21, 34, 55, 89 seems very precise, whereas a nice round number like 20, 40, 60, and 100 seems like what they are - an estimate.
The Fibonacci-like sequence helps teams to recognize uncertainty instead of wasting time trying to produce estimates that might also carry a false degree of confidence.
Power of Two Sequence
The Power of Two sequence is calculated based on 2^n, the sequence includes
2, 4, 8, 16, 32, 64, 128, …
I am including this sequence in this article because this sequence is used in development by some companies. However, I am particularly not a fan of the power of two sequence. The reason is that the sequences grows at a larger scale very quickly and does not leave enough room to estimate a variety of user stories. There is larger difference between 8 to 16 than 8 to 13 and there is larger difference between 32 to 64 than 40 to 60. This larger gap aids in making an inaccurate decision while estimating story points. For example if you think a user story will require 50 user points, choosing either 32 or 64 is way off than choosing 40 or 60.
The Currency Sequence
This sequence includes three seed values and subsequent three values are derived by multiplying the first 3 by 10.
n1, n2, n3
n4 = n1x10, n5 = n2x10, n6 = n3x10
with seed values as 1, 2, and 5. The value of this sequence include the following:
1, 2, 5, 10, 20, 50, 100, 200, 500, ...
All world major currencies are denominated in this sequence. Almost everyone is subconsciously aware of this scale. This scale is easy to remember, as it does not depend on artificial or hard to remember numbers.
Author
Jagmeet Singh writes about Technology and Business on W3Courses.com. Jagmeet is the owner of Parallel Exchange and developed Phonora Photo Galley software product. In his spare time he enjoys photography and loves to travel.
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Agile, Scrum, Story Points, User Stories, s
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