Cumulative Flow Diagram

Cumulative Flow Diagram: Complete Guide

What is a Cumulative Flow Diagram?

A Cumulative Flow Diagram (CFD) is a visual management tool that illustrates the flow of work through different stages of a process over time. It's a stacked area chart that shows the number of work items in each state of a workflow, with time on the x-axis and the count of work items on the y-axis.

Why is the Cumulative Flow Diagram Important?

CFDs provide valuable insights into the workflow health by:
• Visualizing work in progress (WIP)
• Identifying bottlenecks and constraints
• Showing average lead time
• Indicating workflow stability
• Demonstrating delivery rate (throughput)
• Forecasting completion based on historical data

How Cumulative Flow Diagrams Work

A CFD tracks work items as they move through various states in a process. Each colored band represents a specific workflow state (e.g., To Do, In Progress, Testing, Done). The vertical distance between bands shows the number of items in each state at any given time.

Key Components:

1. Workflow States: Represented by colored bands stacked on top of each other.

2. Work in Progress (WIP): The vertical distance between the lowest band (typically "Done") and the highest band (typically "To Do") at any point in time.

3. Lead Time: The horizontal distance between when an item enters the system and when it exits. In the diagram, this is represented by the horizontal distance between the entry point and exit point.

4. Throughput: The rate at which items are completed, shown by the slope of the "Done" band.

5. Bottlenecks: Identified by expanding bands, indicating work accumulating in a particular state.

Reading a Cumulative Flow Diagram

• Parallel bands: Indicate a stable process with consistent throughput.
• Widening bands: Suggest work accumulating in that state, potentially indicating a bottleneck.
• Narrowing bands: Show a state that's processing items faster than they're coming in.
• Flat lines: Indicate no new work entering or leaving a state during that period.

Exam Tips: Answering Questions on Cumulative Flow Diagram

1. Identify the scenario: Determine if the question is asking about lead time, throughput, WIP, or bottlenecks.

2. Understand the visual indicators:
• Rising slopes indicate work being added
• Flat areas indicate no change
• Steeper slopes indicate faster processing
• The space between bands represents WIP in each state

3. Calculate metrics when required:
• Lead time = Horizontal distance between entry and exit points
• WIP = Vertical distance between bottom and top bands at a specific time
• Throughput = Slope of the "Done" band

4. Analyze patterns:
• Look for expanding bands (bottlenecks)
• Check for consistent spacing (stable process)
• Note any unusual patterns or discontinuities

5. Relate to Agile principles:
• Connect CFD observations to Kanban principles
• Focus on flow, limiting WIP, and managing bottlenecks
• Explain how observed patterns impact delivery predictability

6. Common question types:
• Identifying bottlenecks in a given CFD
• Calculating approximate lead times
• Determining if a process is stable or unstable
• Recommending improvements based on CFD patterns
• Comparing different CFDs to determine which process is more efficient

7. Practice interpretation:
• Study various CFD examples and practice reading them
• Learn to quickly identify key metrics and patterns
• Connect visual patterns to real-world workflow situations

Remember that in an exam context, the CFD is primarily used to assess your understanding of flow, identify process issues, and demonstrate knowledge of how to improve workflow efficiency in Agile environments.