Skip to main content

Velocity Calculus - The mathematical study of the changing software development effort by a team


In the practice of Scrum many people appear to have their favorite method of calculating the team's velocity. For many, this exercise appears very academic. Yet when you get three people and ask them you will invariability get more answers than you have belly-buttons.


Velocity—the rate of change in the position of an object; a vector quantity, with both magnitude and direction.
“Calculus is the mathematical study of change.” — Donald Latorre 

This pamphlet describes the method I use to teach beginning teams this one very important Scrum concept via a photo journal simulation.

Some of the basic reasons many teams are "doing it wrong"... (from my comment on Doc Norton's FB question: Hey social media friends, I am curious to hear about dysfunctions on agile teams related to use of velocity. What have you seen?


  • mgmt not understanding purpose of Velocity empirical measure;
  • teams using some bogus statistical manipulation called an average without the understanding of the constrains that an average is valid within;
  • SM allowing teams to carry over stories and get credit for multiple sprints within one measurement (lack of understanding of empirical);
  • pressure to give "credit" for effort but zero results - culture dynamic viscous feedback loop;
  • lack of understanding of the virtuous cycle that can be built with empirical measurement and understanding of trends;
  • no action to embrace the virtuous benefits of a measure-respond-adapt model (specifically story slicing to appropriate size)
... there's 6 - but saving the best for last:
  • breaking the basic tenants of the scrum estimation model - allow me to expand for those who have already condemned me for violating written (or suggesting unwritten) dogma...
    • a PBL item has a "size" before being Ready (a gate action) for planning;
    • the team adjusts the PBL item size any/ever time they touch the item and learn more about it (like at planning/grooming);
    • each item is sized based on effort/etc. from NOW (or start of sprint - a point in time) to DONE (never on past sunk cost effort);
    • empirical evidence and updated estimates are a good way to plan;
  • therefore carryover stories are resized before being brought into the next sprint - also reprioritized - and crying over spilt milk or lost effort credit is not allowed in baseball (or sprint planning)

Day 1 - Sprint Planning
A simulated sprint plan with four stories is developed. The team forecast they will do 26 points in this sprint.




Day 2
The team really gets to work.




Day 3
Little progress is visible, concern starts to show.


Day 4
Do you feel the sprint progress starting to slide out of control?



Day 5
About one half of the schedule is spent, but only one story is done.



Day 6
The team has started work on all four stories, will this amount of ‘WIP’ come back to hurt them?




Day 7
Although two stories are now done, the time box is quickly expiring.


Day 8
The team is mired in the largest story.



Day 9
The output of the sprint is quite fuzzy. What will be done for the demo, what do we do with the partially completed work?



Day 10
The Sprint Demo day. Three stories done (A, B, & D) get demoed to the PO and accepted.



Close the Sprint
Calculate the Velocity - a simple arithmetic sum.




Story C is resized given its known state and the effort to get it from here to done. 




What is done with the unfinished story? It goes back into the backlog and is ordered and resized.




Backlog grooming (refinement) is done to prepare for the next sprint planning session.





Trophies of accomplishments help motivation and release planning. Yesterday’s weather (pattern) predicts the next sprints velocity.


Sprint 2 Begins with Sprint Planning
Day 1
Three stories are selected by the team.  Including the resized (now 8 points) story C.


Day 2
Work begins on yet another sprint.


Day 3
Work progresses on story tasks.


The cycles of days repeats and the next sprint completes.


Close Sprint 2
Calculate the Velocity - a simple arithmetic sum.



In an alternative world we may do more complex calculus. But will it lead us to better predictability?


In this alternative world one wishes to receive partial credit for work attempted.  Yet the story was resized based upon the known state and getting it to done.




Simplicity is the ultimate sophistication. — Leonardo di Vinci 

Now let’s move from the empirical world of measurement and into the realm of lies.








Simply graphing the empirical results and using the human eye & mind to predict is more accurate than many peoples math.




Velocity is an optimistic measure. An early objective is to have a predictable team.

Velocity may be a good predictor of release duration. Yet it is always an optimistic predictor.




Variance Graphed: Pessimistic projection (red line) & optimistic projection (green line) of release duration.



While in the realm of fabrication of information — let’s better describe the summary average with it’s variance.








Post a Comment

Most Popular on Agile Complexification Inverter

David's notes on "Drive"

- "The Surprising Truth about what Motivates Us" by Dan Pink.

Amazon book order
What I notice first and really like is the subtle implication in the shadow of the "i" in Drive is a person taking one step in a running motion.  This brings to mind the old saying - "there is no I in TEAM".  There is however a ME in TEAM, and there is an I in DRIVE.  And when one talks about motivating a team or an individual - it all starts with - what's in it for me.

Introduction

Pink starts with an early experiment with monkeys on problem solving.  Seems the monkeys were much better problem solver's than the scientist thought they should be.  This 1949 experiment is explained as the early understanding of motivation.  At the time there were two main drivers of motivation:  biological & external influences.  Harry F. Harlow defines the third drive in a novel theory:  "The performance of the task provided intrinsic reward" (p 3).  This is Dan Pink's M…

Software Development terms applied to Home Construction

Let's Invert the typically wrong headed view of Software Development project management as a construction project.  We can map it the other way just to see if it works... to have some fun, to explore the meaning of phrases we toss around quite frequently.


Normally Project Management terms come from a construction domain.  We are going to apply the lexicon of modern software to the construction of a home.  We will follow the construction project and meet some of the people doing the work.

This is a very small (8 homes from $600,000 skyward) program in my 30-40 year old neighborhood.

About 6 months ago I saw the programs landing page go up.  It gives casual observers and some of the stakeholders a general idea of the intent of the program.  And most importantly who to contact for additional information if you happen to be interested in their products.

The Refuge program has 8 product projects and has them running independently.  Yet much of their DevOps infrastructure has already b…

Innovation in the Automobile Industry

In the 1900s the automobile industry was the most important and innovation industry in the USA.  But one could question if this was good for our society in the long run.  And one could question if they actually innovated.

In the early 1900s there were few automobiles, very little infrastructure created to support the industry.  For example the road system was still designed for horse drawn wagons and the wagon wheel (remember a steal rim and wooden compression spoke wheel).  The future US Highways, or the 1950s Interstate Highway System at the cost of $425 billion were decades and many innovations away. There was no gas service station, there were however horse stables, farriers, and blacksmiths in each town along the roads.  There was no real "road map", there was no road naming system, like was created in 1926 - the United States Numbered Highway System.

The industry employees millions of people, and was a large factor in the economy of the USA.  It created or was created b…

Where is Shakespeare When We Need Him?

We are desperately searching for a term for people that connotes the best of human kind.  The creative, sensing, combinatorial synergistic, empathic solutioning persons that have yet to been labeled with a role name that works.

Some of the old terms:
Staff, Workforce, Human Resource, My Team, Army, Company

Shakespeare created 1700 words in his time.  He mutated verbs to nouns, and vice-a-versa, transformed verbs into adjectives, and formed words from whole cloth never before heard.  This skill is rare, but there is a poet that can create the term we need in the twenty-first century.

What should this term define?

21st Century Human Resource; the generalizing specialist.

Yes, but what more?  What less?

Suggest your poetry in the comments, let us see if we cannot do 1/1700 as well as The Bard.

By-the-way; who create the phrase "coin a word"?




Elements of an Effective Scrum Task Board

What are the individual elements that make a Scrum task board effective for the team and the leadership of the team?  There are a few basic elements that are quite obvious when you have seen a few good Scrum boards... but there are some other elements that appear to elude even the most servant of leaders of Scrum teams.









In general I'm referring to a physical Scrum board.  Although software applications will replicated may of the elements of a good Scrum board there will be affordances that are not easily replicated.  And software applications offer features not easily implemented in the physical domain also.





Scrum Info Radiator Checklist (PDF) Basic Elements
Board Framework - columns and rows laid out in bold colors (blue tape works well)
Attributes:  space for the total number of stickies that will need to belong in each cell of the matrix;  lines that are not easy eroded, but are also easy to replace;  see Orientation.

Columns (or Rows) - labeled
    Stories
    To Do
    Work In P…