Root cause analysis using cause effect diagrams

Categories Agile
Cause effect diagram

A guaranteed way to waste our efforts when trying to fix a problem is to attempt to fix the symptoms rather than the root cause. Sure, we may be able to make the problem go away but as the root cause still is there, the problem is likely to come back. Either, we will encounter the same issue again or some different problem will pop up.

The most well-known method for root cause analysis is the simple but surprisingly effective “5 Whys” method. This method suggests that the root cause of almost any problem can be found through simply asking the following 5 questions:

  1. Why?
  2. Why?
  3. Why?
  4. Why?
  5. Why?

Often, this simple method is all we need to do to get to a cause worth solving. We don’t even need to get that hung up on the number 5. Sometimes, we might get there in 4 “whys”, sometimes it may take six. The point is to dig deeper than what we would otherwise do.

Sometimes, though, a slightly more thorough analysis may be required needed. This is where cause effect diagrams come in. I first came across this method in Henrik Kniberg’s excellent book Lean from the Trenches and have been a fan ever since.

This is a great tool that you can either use on your own (I use it sometimes to help me get my head around problems) or with a group, for example in a sprint retrospective.

How to create cause effect diagrams

The method based on the same idea as “5 whys”, but slightly more refined.

  1. Start by writing the problem you’re trying to solve on a sticky note and place it in the middle of a whiteboard.
  2. To understand more about the problem and to find out whether it is a problem worth solving, ask “So what?”. Why does the problem matter? List a few effects of the problem, place them on the whiteboard and draw arrows from the first sticky note.
  3. Digging into causes of the problem by writing answers to “Why?” on sticky notes and draw arrows.
  4. Repeat, digging deeper into each effect or cause as you see fit.
  5. Identify the root causes you want to address and possible solutions to these.

When we struggle to answer “why?” for something, chances are you’ve encountered a root cause.

Sometimes, we end up with loops in the Cause Effect Diagram. These are vicious circles. Highlight them with double arrows or a red pen. An example:

Cause effect diagram loop

We release infrequently. Therefore, each release ends up containing a lot of user stories. Big releases are scary, so we deploy less frequently.

Breaking self-amplifying circles like this can have a big effect so this may be one area to focus your improvement efforts on.

Conclusion

Cause effect diagrams are a great way to analyse and visualise a problem. It will not only help you find causes but also the effects, to help you understand why – or if – it is important to solve the problem.


Do you have experiences using cause effect diagrams or do you have any other tools you use for root cause analysis? Share your experiences in the comments below!

 

 

Magnus Dahlgren – Scrum Master (CSP) and aspiring Agile Coach

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