Getting the most value out of a process is important to any leader.  Balancing getting the most value with getting value sooner complicates the discussion.  In some cases, getting some value sooner is worth more than the same value delivered later.  Guiding the delivery of value is more complicated than a rank ordering a list of user stories and then magically hoping that everything will happen in the most effective and efficient manner possible.  Measurement is an important tool to help team and organizations ask the right questions.  To borrow an idea from Daniel Vacanti’s Actionable Agile Metrics for Predictability, measurement helps people ask the right questions sooner.  The following 6 flow metrics provide process transparency into organizations that leverage continuous flow, scrumban, and/or Scrum as the basis for their Agile implementations. 

  1. Work in progress
  2. Story Escape Rate
  3. Cycle time (two ways)
  4. Throughput
  5. Velocity

The six flow metrics while useful in their own right, provide even more transparency when link via Little’s Law.  In a recent entry of our re-read of Actionable Agile Metrics for Predictability (Chapter 3) we discussed an overview of Little’s Law.  The assumptions that allow Little’s Law to hold for flow metrics are an excellent definition of the discipline needed to make Agile techniques effective and efficient (in addition to being responsive).  The six flow metrics provide useful feedback to teams about the process compromises that teams are making in the heat of delivery.  The basic assumptions Vacanti identified are:

  1. Average input and output are equal.
  2. All work started is completed.
  3. WIP should roughly be the same at the beginning and end of the period being measured. (This will not be true under Scrum – which follows of an s curve)
  4. Average age of WIP is not increasing
  5. WIP, cycle time and throughput are measured using consistent units of measure.

Assumptions 1 and 2 reflect conservation of flow.
Assumptions 3 and 4 equate to system stability
The 5th assumption is all about the math.

Metrics:

Work in progress (WIP) is defined as the amount work that has arrived to be worked on in a system and has not yet exited the system regardless of whether the item is actively being worked on or being delayed.

Formula:

WIP = total number of stories accepted into the sprint at ANY time between start and end of the sprint that is not done (deployable).

WIP should be tracked on a daily basis.

Notes:

  •         In a Scrum based approach, WIP will begin at zero and end at zero.  In continuous flow or Kanban, the WIP should be relatively constant.  (Test assumptions 1 and 3)

Story Escape Rate (SER) is defined the number of stories can are not done (deployable) by the end of the sprint

Formula:

SER = Stories Not Done / (Stories Done + Stories Not Done)

Review at retrospective and publish to other teams.

Notes:

  •   All work started should be completed in a single sprint.  This is metric is oriented to Scrum or Scrumban.  SERs greater than zero (especially if widening) need to addressed in team retrospectives.  (Tests assumption 2)

The first two metrics provide feedback about the efficiency of the process being used to deliver value.  As importantly these metrics help teams to understand whether they are being disciplined enough so they are predictable. In Part 2 we will tackle:

  • Cycle time (two ways)
  • Throughput
  • Velocity