The Cause and Effect diagram is also known as a fish bone diagram, because it resembles the skeleton of a fish. Using a cause and effect diagram can be the most effective way to define the problems that you intend to solve with your product. Get your stakeholders engaged in your program with this compelling visual!
Getting To The Root Of The Problem
In our recent article about writing good problem statements, we pointed out a common mistake people make with problem statements – they confuse the manifestation of a problem with a problem.
Problem manifestation [noun] – an example of a way in which a problem is exhibited, without appreciating the true nature of the problem. Ex: The problem manifestation is that the tires on my car are under-inflated. The problem is that my car is too expensive to maintain.
This distinction is relevant. The cost of operating the car is too high. That is the problem. It happens to be that one reason that the cost is too high is under-inflated tires. If you focus your energy on getting properly inflated tires, it will help (by improving fuel economy a little, and by reducing the frequency of tire replacement) with costs anecdotally. But you will not have solved the problem that costs are too high. Unless you get lucky. Costs can be high because the engine is inefficient or damaged, the aerodynamics of the car are bad, or any of a number of reasons. If you solve the problem by addressing a single manifestation of the problem, without understanding the whole problem, it is only because of luck.
In the comments on that article, The Demon points out that it is not always easy to identify the right level of abstraction for your problem. The cause and effect diagram makes it brilliantly simple not only to get to the root of the problem, but to communicate this cause-and-effect hierarchy of problem decomposition.
Cause And Effect Diagram Example
The cause and effect diagram is so visceral that the easiest way to communicate how it works is to show an example. Here’s what the cause and effect diagram would look like for the example problem above, where the cost of operating the car is too high.
The main problem is that the cost of operation is too high. This is the far-right, or fish-head part of the diagram (it is sometimes called a fish bone diagram).
The problem can be decomposed into three separate problems: spending too much on fuel, maintenance, and payments. Each of those problems can be further decomposed. Note that “under-inflated tires” appears twice – once as a cause of low miles per gallon (MPG) and once as an excess maintenance cost.
Alternately, you could recognize that spending too much on fuel could be due to lower fuel economy or excessively high prices. You could then choose to decompose the problem slightly differently:
Either approach results in crystal clarity that under-inflated tires is one root cause of low fuel economy, which is one cause of excessive spending on fuel, which is one cause of excessive operating costs. This visual approach helps significantly when trying to identify the right level of abstraction for expressing the problems in your problem statement.
Problem Abstraction Is A Side Benefit
The really cool part is that the help you get in finding the right level of abstraction for your problem is just icing on the cake. [Ed: No jokes about fish-bone cake. Ick!]
Someone questioned me once on the value of writing passionate requirements. Show one of these to your team, and you’ll get enthusiastic, passionate responses. You’ll get kudos from the business for demonstrating that you understand their needs. You’ll get praise from the implementation team for providing them with context.
Using Visio To Create A Cause And Effect Diagram
Creating a cause and effect diagram in Microsoft Visio is really easy, there’s a built in template, and it’s a good one. Create a new drawing and select the “Cause and Effect Diagram Shapes” template (under “Business Process”):
Visio will create a new drawing with a blank cause and effect diagram set up for you:
Fill in the boxes with the large problems. To get to the next level of detail (such as “Fuel Economy is Too low” in the last example), select the “Primary Cause” shape and drag it onto the diagram. Attach the arrowhead to one of the branches (the fish “ribs”) and start typing. For once, Visio’s default layout is where you want it.
To get a secondary cause shape (such as “Bad Aerodynamics” in the last example), select the “Secondary Cause” shape and drag it onto the diagram. Attach the arrowhead to the “primary cause” arrow you just created.
You already have a good justification for defining problems at the right level of abstraction. Now you know how to easily create a cause and effect diagram to find the right problem definition. As a bonus, communicating with stakeholders just got a lot easier – include this in your BRD.