What is DOE in Six Sigma & Its Application?


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The Six Sigma model prevents process variation because variation hampers a process’s ability to reliably and consistently deliver high-quality products or services.
The Six Sigma toolbox consists of a wide range of tools that include simple and commonly used tools such as flowcharts, Pareto analysis and diagrams, and more advanced statistical tools such as the design of experiments, regression analysis. One such advanced tool is DOE in six sigma.

What Is the Design of Experiments Six Sigma (DOE)?

The DOE in Six Sigma allows quality teams to study several potential causes of process variation simultaneously. DOE is used to model the X’s (independent variables) concerning Y’s (Variable dependent data). In simple terms, it allows the team to project the effects that the inputs of a process would have on the final output.

What is DOE in Six Sigma & Its Application?

Where do you use DOE in a classic DMAIC model?

Six Sigma follows a DMAIC model consisting of steps: Define, Measure, Analyze, Improve, and Control.
DOE is mainly used in the Analyze and Improve stages of the DMAIC model, the Analyze stage (to analyze the data points) and the Improve stage (to create and evaluate probable solutions).

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Application of Design of Experiments Six Sigma

Let’s take an example from the finance industry. The team is looking for a ‘percentage complete’ of their applicants. The applicants are applying for a health insurance policy, and the application is incomplete; hence the transaction cannot be completed and is stuck in the system. This will result in customer dissatisfaction and a low conversion rate for the company. The Six Sigma team has completed the Design Measure and Analyze phase, and now they are at the Improve phase of the DMAIC model. The Six Sigma Six team categorized the problem into two major subdivisions: the type of application (loan, term insurance, mutual fund) and the number of details to be filled in the application form. The team came up with a potential solution. They decided to describe questions, an example answer, and a negative example.
    Potential Solutions Goal  
Number of Applications Type Description Example Counter Example Percentage of Completed Applications
1 Loan Old Old No example X
2 Health Insurance New description added in the form Yes Yes an Increased number of applications.
100 Loan New Yes Yes After applying these solutions it grew from X
Applying Design Of Experiments Six Sigma, the team would get the percentage complete and the Normal Plot of the effects or a Pareto chart. The Six Sigma team can now understand the impact of their input solutions on the output, which in this case is Percentage Complete. In DOE, we need to define high and low levels. In the above example, the high would be ‘New description’ and ‘Yes,’ low would be ‘Old description’ and ‘No.’

DOE in Six Sigma Terminology

  • Experimental Units= People who filled the applications
  • Response= Percentage of Completed Applications
  • Factors= New description, Type of applications, Counter Example, Examples
  • Level= This is a measure of the degree of modification of a factor.

Types of Factors In DOE In Six Sigma

  • Control factors- Process factors, variables controlled by the team.
  • Blocks- The blocks in the experiment, e.g., the time required to run the experiment.
  • Nuisance factors- These factors do not have a significant effect on the response.

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Benefits Of DOE In Six Sigma

  • Allows you to study the impact that inputs have on each other and helps identify the interactions between inputs that cause the exit condition
  • Focuses on the factors with the most significant impact
  • Reduces costs associated with the experiment
  • Allows the control of the outputs

How To Apply DOE In Six Sigma?

  • Selecting the Factors

    Once the factors have been identified, the team must determine the parameters. With more levels identified for each element, the more trials it will take to test those levels. The more significant the difference between the factor levels, the easier it becomes to measure the variance.


    Setting the Levels

    The number of runs (treatments) depends on the number of resources that can be accommodated, such as time and money. Remember that repetitions are ideal for helping validate results and help detect any unexpected results.


    Evaluating the Response

    Design Of Experiments Six Sigma allows you to modify inputs to determine how they affect responses. Instead of testing one factor at a time while keeping the others constant, the DOE reveals how interrelated factors react over a wide range of values without directly verifying all possible values. This helps demonstrate the causes behind the different factors and levels in a process and allows the team to understand the process much faster. 

    When completed, the Design Of Experiments helps the Six Sigma project team identify the combination of inputs better. DOE in Six Sigma consultants, such as Arrowhead Consulting in India, ensures that your DOE in Six Sigma goals is attained, which leads to the highest quality product or service.



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