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# The Cause & Effect Matrix

One of my favorite continuous improvement tools is the cause and effect matrix (C&E Matrix).  Sometimes you will hear this tool referred to as a XY Matrix.  I am not referring to the Ishikawa Diagram (fishbone) even though some text books and consultants call the Ishikawa Diagram a C&E Matrix.

When to use this tool?

The C&E Matrix can be used for many purposes.  I suppose the most traditional way to use it is to help us narrow a long list of suspected X’s (inputs) down to a more manageable one.  In other words, if after process mapping we identify 42 inputs to a process the practitioner is not likely in position to start investigating each input.  Instead they may use this matrix to determine which of these 42 inputs should be looked at first, second, third, etc.

How to use this tool

The first thing we need to understand is the voice of the customer.  Regarding the project or problem you are working on ask yourself (or better yet ask the customer!) what is important to them?

Once we have these outputs identified we will load them into the matrix as we will soon demonstrate.  Then we assign a “priority factor” to each output.  We normally use a scale of 1 – 10 with 1 meaning the customer cares little about this and 10 being the customer places ultra high priority to this output.

Next, we need to identify the key process input variables for this particular process.  There are a plethora of ways to do this… extract from process maps, hit the gemba (place where the work is happening) and ask folks for their thoughts, etc.

Once these two steps are complete we are now in position to rank how strongly the inputs impact the outputs.  The scale is flexible and some use 1 -10 as discussed above.  Personally, I prefer to use a ranking scheme of 1 (no impact), 3 (little impact), 5 (marginal impact), 7 (strong impact), 10 (very strong impact).

The last thing we do is cross multiply the correlation rankings with the priority factors and sum for each input.  No worries as I am attaching a free MS Excel template that has the formulas already figured out for you!

Example – Green Grass

If you own a home with a yard chances are you want your grass nice and green with no weeds.  Here is how you could use a C&E Matrix to help identify which “inputs” are the most critical.

And before the landscaping gurus come calling I am guessing at these numbers in the example. I am simply trying to use an example most people can relate to demonstrating how the tool works.  I am NOT proposing this is how to make a yard green.  Although I am using personal experience and my grass isn’t too shabby.

Identify & Rank Customer Requirements

The first step is to identify what it is our customer (you and your family in this case) values the most.  In this example the customer is interested in 3 things:

1. Deep green grass (the greener the better).  We rank this 10, or extremely important.
2. Thickness of the grass (the thicker the better).  We rank this 8, not as important as the color, but still very important.
3. No weeds in the grass.  Again, we rank this an 8.

Identify Key Process Input Variables

Next we need to identify the input variables we can control.  After discussing this project with neighbors and family members the following inputs were defined:

• Brand of Lawn Mower
• Cutting frequency
• Watering frequency
• Watering duration
• Fertilizer type
• Fertilizer frequency
• Operator experience

Determine impact of inputs on the outputs

Now that we have our outputs loaded and prioritized as well as our inputs loaded it’s time to see how the inputs impact the each output.  To do this we simply ask the question of how significant each input is to each output.

So, for example, we ask ourselves how much of an impact the fertilizer type has on the color of our grass?  Then how does the fertilizer type impact the thickness of the grass?  And finally, how significantly does the fertilizer type impact the amount of weeds in the grass?  Again, we use a rank of 1-10 or something like 1, 3, 5, 7, and 10.

Using our handy dandy spreadsheet, which does all the multiplying and adding for us, we learn that the following inputs seem to be where we should focus first.

1. Fertilizer type – 260
2. Watering frequency – 220
3. Mower height – 212
4. Fertilizer frequency – 206
5. Watering duration – 204

If I had minimal time and budget these are where I may start in an effort to make my grass as green and thick as possible with no weeds.

It’s all opinions!

This was a simple, and somewhat silly, example.  But let me assure you that the minute you have 128 inputs and are not sure where to start this tool is perhaps the best friend you will ever have.

But the key thing to remember is that this entire tool is based on opinions (unless hard data exists to help us rate the potential impact of an input on an output).  Therefore, it is absolutely critical to have a cross functional team help you.  If you try to sit at your desk and work this out yourself chances are you will be way off… even if you are an expert in the area.

Next up

Tomorrow night I will share some different ways to use this tool.

Free C&E Matrix Template

Here is a free C&E Matrix Template for your use.  Save the file to your computer and then open it.

Feel free to share this template with as many people as you want.  I plan to begin offering free templates… which was one of the reasons I wanted to get a self hosted blog!  Please let me know if you have any problems downloading the file and I will email it to you.

Hi!
I was always a little confused about having to many inputs…the advice that I had from my LSS trainer was to use process steps instead of inputs in this case…but then it becomes too loose.
What can you suggest?

• Only listing the process step is bad advice, in my opinion, and will lead to problems… I highly suggest listing each input for each process steps. Continuous improvement is hard work… there are no short cuts I’m afraid.

Thank you, Ron!
You just confirmed my guess!
I am a recent certificant, so I am still collecting experience and best practices….
I thing it is ok to funnel down to 50% of initial KPIV’s, you can then use FMEA as next funnel.