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EEM332

EEM332. Design of Experiments. Design of Engineering Experiments Part 1 – Introduction Chapter 1, Text. Some basic principles and terminology The strategy of experimentation Guidelines for planning, conducting and analyzing experiments. Introduction to DOX.

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EEM332

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  1. EEM332 Design of Experiments DOX 6E Montgomery

  2. Design of Engineering ExperimentsPart 1 – IntroductionChapter 1, Text • Some basic principles and terminology • The strategy of experimentation • Guidelines for planning, conducting and analyzing experiments DOX 6E Montgomery

  3. Introduction to DOX • An experiment is a test or a series of tests • Experiments are used widely in the engineering world • Process characterization & optimization • Evaluation of material properties • Product design & development • Component & system tolerance determination • “All experiments are designed experiments, some are poorly designed, some are well-designed” DOX 6E Montgomery

  4. Engineering Experiments • Reduce time to design/develop new products & processes • Improve performance of existing processes • Improve reliability and performance of products • Achieve product & process robustness • Evaluation of materials, design alternatives, setting component & system tolerances, etc. DOX 6E Montgomery

  5. The Basic Principles of DOX • Randomization • Running the trials in an experiment in random order • Notion of balancing out effects of “lurking” variables • Replication • Sample size (improving precision of effect estimation, estimation of error or background noise) • Blocking • Dealing with nuisance factors DOX 6E Montgomery

  6. Strategy of Experimentation • “Best-guess” experiments • Used a lot • More successful than you might suspect, but there are disadvantages… • One-factor-at-a-time (OFAT) experiments • Sometimes associated with the “scientific” or “engineering” method • Devastated by interaction, also very inefficient • Statistically designedexperiments • Based on Fisher’s factorial concept DOX 6E Montgomery

  7. Strategy of Experiments Example: The golf experiment: • Type of driver (regular or oversized) • Type of ball (balata or three-piece) • Walking vs. riding • Type of beverage (water or beer) • Time of round (morning or afternoon) • Weather (cool or hot , windy or calm) • Type of golf spike (metal or soft) • Etc, etc, etc… DOX 6E Montgomery

  8. Strategy of Experiments Best Guess ? Select and arbitrary combination of factors, test them and observe. Change the level of factors based on observations Example: Select oversized driver, balata ball, golf cart and water as beverage and the resulting score is 87. It was observed that there were several wayward shots with the big driver. Therefore, change to regular-size driver and play again.. What is your assessment on this approach? Can we guarantee that we can arrive at the BEST combination? DOX 6E Montgomery

  9. Strategy of Experiments One factor at a time ? Riding, regular size driver and drinking water improve the score Type of ball has no effect What is your assessment on this approach? DOX 6E Montgomery

  10. Strategy of Experiments If use regular-sized driver, type of beverage has no effect If use oversized driver, type of beverage has an effect Interaction between factors DOX 6E Montgomery

  11. Strategy of Experiments Factorial ? Factors are varied together and observe the joint effects Example: A two-factor factorial experiment 22 factorial design DOX 6E Montgomery

  12. Factorial Designs • In a factorial experiment, allpossiblecombinations of factor levels are tested • The golf experiment: • Type of driver • Type of ball • Walking vs. riding • Type of beverage • Time of round • Weather • Type of golf spike • Etc, etc, etc… DOX 6E Montgomery

  13. Factorial Design DOX 6E Montgomery

  14. Factorial Design The effect of switching from oversized driver to regular-sized driver Driver effect = (92+94+93+91)/4 - (88+91+88+90)/4 = 3.25 DOX 6E Montgomery

  15. Factorial Design Ball effect = (88+91+92+94)/4 - (88+90+93+91)/4 = 0.75 DOX 6E Montgomery

  16. Factorial Design Interaction effect = (92+94+88+90)/4 - (88+91+93+91)/4 = 0.25 DOX 6E Montgomery

  17. Factorial Designs with Several Factors DOX 6E Montgomery

  18. Factorial Designs with Several FactorsA Fractional Factorial DOX 6E Montgomery

  19. Planning, Conducting & Analyzing an Experiment • Recognition of & statement of problem • Choice of factors, levels, and ranges • Selection of the response variable(s) • Choice of design • Conducting the experiment • Statistical analysis • Drawing conclusions, recommendations DOX 6E Montgomery

  20. Assignment 1 Conducting an experiment on in groups DOX 6E Montgomery

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