Christophe MontagneInterim CTO · Advisory

Scrum in Name Only/Part I · Foundations·2 min read

03A common ancestor

Deming's improvement cycle behind both PMBOK and Scrum, and Scrum as a set of nested loops.

PMBOK and Scrum are usually presented as rivals. Their family tree tells a different story: both descend from the same idea of managing work through feedback.

Walter Shewhart formulated the cycle in the 1930s, and W. Edwards Deming popularised it, first in post-war Japan and later in the West: plan, do, check, act. Deming preferred "study" to "check", because the step means comparing results with a prediction and learning from the gap.

Earlier editions of the PMBOK Guide state explicitly that the interaction between its process groups follows the plan-do-check-act cycle. Planning is plan, executing is do, monitoring and controlling covers check and act. The whole project is one large loop, with a continuous control loop running inside it.

Scrum's lineage runs through the same ground. Its name comes from Takeuchi and Nonaka's 1986 Harvard Business Review article on Japanese product development, a culture deeply shaped by Deming's teaching. Ken Schwaber and Jeff Sutherland presented Scrum in 1995 as an application of empirical process control, which the Scrum Guide summarises in three pillars: transparency, inspection and adaptation. That is the improvement cycle under another name.

The difference is the scale and frequency of the loops. Scrum runs several of them, nested inside one another.

Scrum as nested improvement loops The product horizon contains sprints. Each sprint maps sprint planning, the work, the sprint review and the retrospective to plan, do, check and act. Inside the work, the Daily Scrum runs a 24-hour loop. Product horizon Months · Product Goal, roadmap, release forecast Sprint One month or less · Sprint Goal PLAN Sprint planning DO Build the increment CHECK Sprint review ACT Retrospective Daily Scrum 24-hour loop Inspects the product, updates the backlog Inspects the process, changes how we work Next sprint Each increment tests the product hypothesis against the Product Goal
Figure 1 · Scrum as nested improvement loops. The sprint runs two inspections side by side: one on the product, one on the way the team works.

Two details matter for what follows. First, the sprint runs two distinct check-and-act cycles. The review inspects the product and changes what will be built. The retrospective inspects the process and changes how it will be built. The second loop is the closest to Deming's own concern, which was improving the system rather than the output.

Second, every loop needs something to inspect against. The daily inspects progress towards the Sprint Goal. The review inspects the increment against the Product Goal. Remove the goal and the loop has nothing to compare, so it falls back to reporting activity. We will return to this in Part II.

The analogy also has limits, and they are instructive. Deming applied the cycle mostly to repeatable processes, to reduce variation. Scrum applies it mostly to product discovery under uncertainty. And Deming's management principles, which include driving out fear and eliminating numerical quotas, are routinely violated in his name when velocity becomes a target or a sprint forecast is enforced as a contract.

Section takeaways

  • PMBOK's process groups and Scrum's empiricism both descend from the plan-do-check-act cycle.
  • PMBOK runs one large loop around the project; Scrum runs several nested loops at different frequencies.
  • Every loop needs a goal to inspect against. Without one, the rituals turn into status reporting.