## What is a Cause and Effect Matrix?

Cause and effect matrix is a six sigma tool uses to prioritize the key process input variables (KPIVs) based on priorities of customer outputs (KPOVs). In other words it establish the correlation between process input variables to the customer’s outputs during root cause analysis.

Cause and effect matrix also called X-Y diagram, Prioritization matrix and correlation matrix. The objective of cause and effect matrix is to mathematically compute the correlation between key process input variables (X’s) and Customer outputs (Y’s).

Cause and effect analysis, process flow map and information about voice of customer are the pre-requisites for cause and effect matrix.

A cause-and-effect matrix can be used to evaluate and document relationships between input and output variables. This method is also very much similar to the Quality Function Deployment. It objectively evaluates the team’s subjective opinion about the KPIVs.

## When Would You Use an X-Y Diagram in the DMAIC Process?

Cause and Effect matrix is a great tool for prioritizing a long list of possible things and especially uses in the Measure phase of the DMAIC project . This method also used to determine the primary factors for experiments in DOE and also to determine the objective of the Matrix Diagram & FMEA.

In a process all the input variables might influence the outcome, but all the input variables are not equally important. Hence develop a mathematical model to concentrate the important input variables with respect to the customers output. Cause and effect matrix helps to identify such key input variables.

## How Do You Use It?

**Step 1:** First identify the customer requirements or in other words understand the voice of customer. This can be collected by conducting surveys, focus groups and other means to collect their priorities. Place those priorities in at the top of the X-Y diagram

**Step 2:** Assign priority factor for each of the customer outputs. Generally use 1-10 scale, where 1 being the low priority and 10 being the high priority to the customer

**Step 3:** List all possible key input variables or the improvement factors of the process in each row, those are the Xs in the X-Y diagram

**Step 4:** Assess the relationship between key input variables to the customer outputs and rank each input variables accordingly. Recommended to use geometric progression scale (0,1,3 and 9) where 0 being no impact, 1-low impact,3-medium impact and 9- Input has strong impact or correlation on output

**Step 5:** Cross multiply the customer output priority numbers with correlation rankings and sum the each row at extreme right column

**Step 6:** Finally, determine the rank based on the highest sum total and highlight the critical few variables. This will help to identify the improvement areas.

## An Example of an X-Y Diagram.

XYZ coffee shop franchise at San Diego downtown area reporting sales de-growth for the past 6 months. Six sigma team conducted root cause analysis and also they want to see the key process inputs that are impacting the process.

- Conducts customer survey and identified key customer requirements

- Assign priority factor for each of the customer outputs.

- List all possible key input variables

- Assess the relationship between key input variables to the customer outputs and rank each input variables accordingly

- Cross multiply the customer output priority numbers with correlation rankings and sum the each row

- Ex: for coffee flavor = 9*9+3*6+3*3+9*3+1*4 = 139

- Finally, determine the rank based on the highest sum total and highlight the critical few variables.

## Benefits of Cause and Effect Matrix

- It helps to include customer inputs for decision making
- Visually depict the correlation between key input variable to the customer out puts
- Priority ranking method helps to take the decision based on score rather than individual opinions
- Data collection cost may reduce by ignoring non key process inputs
- Helps to list all the input variables required for the process

## Comments (6)

Hi Ted could not find the sixsigma.org website that was in the video. Can you provide the link?

Hi Dan,

I found the link but it looks like the website was abandoned. Worse yet, the website that is now in its place is entirely infested with ID theft software.

So, I won’t post the link, but I can see what I can do about creating a download similar to what they show here. Is that what you were looking for?

Best, Ted.

Hi Ted,

Could you please explain what decision can be made in the Coffee Shop example once you have the ranks?

Are we saying that only the top three will be the focus of the SS project?

Also, what happens when the Xs might not be completely independent? For example, the “beans freshness” affects the “coffee flavour”?

Many thanks.

Hello Varun Pai,

The objective of cause and effect matrix is to mathematically compute the correlation between key process input variables (X’s) and Customer outputs (Y’s).

In a process all the input variables might influence the outcome, but all the input variables are not equally important. Hence develop a mathematical model to concentrate the important input variables with respect to the customers output.

There is no hard and fast rule to take only top 3. Based on customer importance, you can consider top priority Xs. It helps to include customer inputs for decision-making.

Basically, priority ranking method helps to take the decision based on score rather than individual opinions.

If any of the Xs are dependent, you can consider both for the implementation of process improvements or corrective actions.

Thanks

Ramana

Thank you for the great example of the X-Y diagram!

Glad it was helpful, Barbara!