Predicting Impediments Using Cumulative Flow Diagram(CFD)
A Cumulative Flow Diagram (CFD) is a tool used in queuing theory. It is an area graph that depicts the quantity of work in a given state, showing arrivals, time in queue, quantity in queue, and departure. That’s the reason Cumulative Flow Diagram is a fundamental tool of Kanban method. It allows the team to visualize their effort and the progress. When there’s an impediment about to occur within the process — this is where you’ll see it first. Instead of the graph staying smooth and gently rising, there will be a bump, a sudden ascend or descend. So, as far as predicting problems goes, this is the tool you need.
Cumulative Flow Diagram is a great way to visualize your project/program workflow as it shows the various statuses of work items for an application, version, or sprint. The horizontal x-axis in a CFD indicates time, and the vertical y-axis indicates cards (issues). Each colored area of the chart equates to a workflow status (i.e. a column on your board).
In CFD-1 diagram the horizontal arrow shows us that items added to the backlog on day 3 took on average 8 days to reach production. About half of that time was testing and backlog. We can see that if we were to limit the WIP in Test and Backlog we would significantly reduce the total lead time. The slope of the dark-blue area shows us the velocity (i.e. number of items deployed per day). Over time we can see how higher velocity reduces lead time, while higher WIP increases lead time.
The CFD can be useful for identifying bottlenecks. If your chart contains an area that is widening vertically over time, the column that equates to the widening area will generally be a bottleneck. It is one of the most advanced analytics for Lean management as it provides a concise visualization of the four most important metrics of your flow:
• Lead time is the time between the initiation and delivery of a work item
• Cycle time is the time between two successive deliveries
• Throughput is the rate at which items are passing through the system
• WIP — Work in progress, work that has been started, but not yet completed
CFD-2 is another such example from a real time Agile project, where it shows sprint specific scoped/planned, in progress (WIP) and completed user stories. You can easily observe the bottlenecks here —
a) The planning or sprint scope needs to be revisited and should be aligned to the sprint velocity. It shows consistently bad planning, may be for some specific reason. The Scrum Master should work with the product owner and team in explaining the definition of the sprint backlog and mentor the team for adequate sprint planning.
b) Also the other bottleneck is BU Review, as consistently many stories are in waiting status for BU Review. That gives the insight to management either to control the development or add more business resources for testing.
The main purpose of CFD is to show you how stable your flow is and help you understand where you need to focus in order to make your process more predictable and optimized. It gives you both quantitative and qualitative insight into both past and existing problems and can visualize massive amounts of data for accuracy. I found it very helpful for my projects, let me know if so do you.
