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Experimental Design

Experimental Design. Anthony E. Butterfield CH EN 4903-1. “Research is what I'm doing when I don't know what I'm doing. ” ~ Wernher Von Braun (1912 – 1977). Announcements. Schedule preliminary exam before next lab period so you can get started Wednesday. Start writing now.

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Experimental Design

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  1. Experimental Design Anthony E. Butterfield CH EN 4903-1 “Research is what I'm doing when I don't know what I'm doing. ” ~ Wernher Von Braun (1912 – 1977)

  2. Announcements • Schedule preliminary exam before next lab period so you can get started Wednesday. • Start writing now. • Introduction, theory, materials and equipment table… • Draft of a new Projects Lab web page:http://www.che.utah.edu/projectslab/ • Has updated SOPs for some of your experiments.

  3. Experimental Design • Terminology. • Precautions. • Factorial Design of Experiments. • Put It to Use.

  4. Terminology • Numeric Factors: Variable inputs to a process. For example: pressure, temperature… • Categorical Factors: Discrete inputs to a process.For example: equipment model, chemical substance… • Responses: Effects of changes in factors.For example: Reaction rate increases with temperature and catalyst. • Interactions: The influence of factors on each other.For example: (drinking, driving) vs (drunk driving)

  5. Precautions • Controls. • Why spend the time and resources? • How would you decide if changing a factor gave results significantly different from control experiments? • Randomizing. • Sampling. • When time is a possible factor. • Blindness. • You can be easily fooled by yourexpectations, wants, and pre-conscious processing of data. • Repetition. • In your lab and others.

  6. Experiments for Your Projects • Group A – Immortal Yeast? • Group B – Dirty Hydrogels? • Group C – The Purple CSTR? • Group D – CO2 Absorber? • Group E – Stage Control?

  7. Experimental Design • In my lab, we want to know the effect of temperature, pressure, and time on microbubble volume. • One option:

  8. What Have We Actually Pinned Down? • 3 factors. • 18 experiments. • So, what is the problem? • Repeatability? • Effects? • Interactions?

  9. Factorial Design • 2-Level Factorial with center points. • Some information about repeatability. • Some information about curvature. • Box-Behnken • 3 Factors. • 3 Levels. • 12 Experiments plus center points. • Spherical and so extrapolation is less prone to error. • 2-Level Factorial • 2 Levels, x • 3 Factors, y • 8 tests, (xy) • Larger volume analyzed. • Effect of factors at multiple surfaces. • Some information on interactions.

  10. Why Ignore This Advice?

  11. Competitive Experimental Design • What are the factors? • Numeric or categorical? • Are there interactions? • Each team can perform10 experiments. • Develop a model. • Take 15 shots at the opposing team’s target.

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