A basic introduction to Design of Experiments (DOE) explaining how it works, the benefits of using it and how to use a common DOE application (MiniTab)

1. Mark D. Harrison
sixsigmadude@gmail.com

2. What is a Designed Experiment?
 A systematic procedure carried out under controlled
conditions in order to discover an unknown effect, to
test or establish a hypothesis, or to illustrate a known
effect.
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3. Why use DOE?
 Reduce time to design/develop new products and processes
 Compare Alternatives
 Identify significant Inputs (Factors) affecting an Output
(Response) also known as “Separating the Vital Few from
the Trivial Many”
 Reducing Variability
 Establish a Minimum, Maximum or Target of a Response
 Achieve Product and Process Robustness
 Balancing tradeoffs
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4. A Brief History of DOE
 1918 – 1940s
 R. A. Fisher and Co – Workers
 Used extensively in Agricultural science
 Factorial Design and ANOVA
 1050s to late 1970s
 1st Industrial era
 Box & Wilson, Response Surfaces
 Chemical and Process Industries
 1970s – 1990s
 2nd Industrial era
 Quality improvement initiatives in many industries
 CQI and TQM became company goals
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5. Approaches to Experimentation
 Trail and Error
 Change One Separate Factor at a Time (C.O.S.T.)
 Design of Experiments (DOE)
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6. Trail and Error Example
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7. C.O.S.T Example
 2 Factors
 Volume of Reaction Chamber
 pH of the Solution
 Output / Response
 Yield
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8. Reaction Volume
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You can see the highest yield is about 550 ml
Volume incremented in 50ml steps

9. pH of Solution
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pH is incremented by .5 units
You can see the highest yield is at about a pH of 4.5

10. Plot the Data
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Point #10 is what we think is the highest yield

11. The Real Process
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Our experiment location is on the edge of the highest yield possible

12. What DOE shows us
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Our optimum is not a process optimum
Which direction to experiment next

13. DOE vs C.O.S.T.
 Better approach to experimenting
 DOE suggests # of runs, usually less than C.O.S.T.
 DOE provides a model for the direction to follow
 Many factors can be used, not just two
 Benefits of DOE
 An organized approach that connects experiments in a
rational manner
 The influence of and interactions between all factors can be
estimated
 More precise information is acquired in fewer experiments
 Results are evaluated in the light of variability
 Support for decision-making: map of the system (response
contour plot)
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14. Components of DOE
 Factors / Controllable Variables)
 Variables you can change (Time, Temperature, etc..)
 Levels
 Where Factors are set (2 minutes, 100 degrees, etc)
 Responses
 Outputs of your process (yield, dimension, weight, etc)
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15. The DOE Process
 Define the Objective
 Define the Process and select Factors to be studied
 Select a Response and Measurement system
 Select an Experimental Design
 Execute Experiments accurately
 Check results for any issues
 Model data
 Verify predicted results with confirmation
experiments to validate model
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16. Types of DOE
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17. Orthogonality
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18. Orthogonality and DOE
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19. Doe Example
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20. The Minitab Tutorial
 Purpose
 Investigate two factors that might decrease the time that is
needed to prepare an order for shipment: the order-
processing system and the packing procedure.
 Factors
 Order Processing System
 Packing Procedures
 Levels
 Current/Proposed
 A / B
 Responses
 Time to prepare order for shipment
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21. Select a Design
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22. Display Available Designs
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23. Complete Design Selection
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24. Details of Design
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25. Factor and Level Names
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26. Randomize and Store Design
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27. View the Design
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28. Enter Experiment Data
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29. Fit the Model
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30. Select Model Terms
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31. Select Analysis Graphs
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32. Factorial Regression
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33. Factorial Regression
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34. Interpret the Probability Plot
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35. Example Effects Plot
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Significant

36. Interpret the Pareto Chart
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37. Additional Analysis
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38. Create Factorial Plots
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39. Main Effects Plot
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40. Interaction Plot
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41. Predict the Response
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42. Prediction for Hours
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99% ?

43. Save the Project
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44. DOE Software Providers
 Minitab
 Minitab 18 Data Analysis
 Minitab Quality Companion Project Management
 Sas JMP
 Sas JMP Data Analysis
 Statgraphics
 Centurion 18
These companies provide free 30 day trails of their software
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45. DOE References
 One Factor at a Time vs DOE Veronica Czitrom
 Design of Experiments – Moresteam
 DOE Upendra Kartik
 Minitab Blog
 DOE Umetrics
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