PMP lesson · Agile Metrics & Events · Agile metrics · lesson 4 of 5 · about 6 minutes
The cumulative flow diagram: spotting bottlenecks
Agile, KanbanFree preview
Goal: After this lesson you can read a cumulative flow diagram, find a bottleneck, and choose the right response.
1The situation
Developers are always busy
The MES Kanban team says they are “always busy”. The cumulative flow diagram tells a more precise story: the ‘In test’ band has been getting wider for six weeks, ‘Done’ rises slowly, and the ‘In development’ band is stable.
The developers are busy creating a pile in front of testing. Being busy is not the same as delivering.
2What a CFD shows
A cumulative flow diagram stacks the number of items in each stage over time. Each coloured band is one stage.
Width
Items in a stage
A wider band = more items waiting or in progress there.
Top of Done
Throughput
How fast items are finished.
Horizontal
Lead time
The distance across the bands at one height.
A widening band = a bottleneck in that stage. Respond with WIP limits and by helping that stage, not by starting more work upstream.
3A widening test band
Test grows wider every day: work is arriving faster than it is tested.
4How it looks on the exam
Exam-style question 1. A Kanban team's cumulative flow diagram shows the 'In test' band widening steadily for six weeks, while 'Done' rises slowly and 'In development' is stable. Developers report being 'always busy'. What does this indicate?
A. Developers are under-utilised
B. Testing is a bottleneck; apply or tighten WIP limits and help move work through testing
C. Velocity is too low; use overtime
D. The diagram is unreliable
Show the answer and the decode
Answer: B.
In simple English
One band keeps widening.
What is the question really asking?
What it means and what to do.
Key words / trigger
“'In test' band widening”
PMP logic
A widening band shows a bottleneck; limit WIP and swarm.
Why the wrong answer looks attractive
'Everyone is busy' sounds productive, but busy is not the same as finishing.
5Remember this
Your memory card
CFD = items per stage over time
Widening band = bottleneck
Respond with WIP limits and swarming, not more starts