On the Role of Decision Analysis in Engineering Design

1. On the Role of Decision Analysis in Engineering Design Sundar Krishnamurty Department of Mechanical and Industrial Engineering University of Massachusetts-Amherst Email: skrishna@ecs.umass.edu 2000 DBD Workshop

2. Should all design activities be constructed under a decision theory framework?

3. 0%  A 0%  A 50%A 17%A 80%A 42%B 14%B 33%B 33%B 20%B 14%C 17%C 17%C 17%C 0%  C 57%D 25%D 17%D 0%  D 0%  D 17%E 0%  E 0%  E 14%E 17%E 1. The fundamental element of engineering design is decision making. All design activities, including those in concept generation, need to be constructed under the decision theory framework. Therefore decision analysis is the most important aspect of design. 2. Design involves both art and science. While the majority of activities are desired to be logical, some activities are intuitive such as brainstorming for the generation of design alternatives which heavily relies on creativity. Decision analysis can support design activities that are logical, however, other theories and techniques need to be developed to enhance intuitive activities. 3. There are benefits and limitations of decision analysis throughout the design process. Based on the design situation, a designer need to decide how to use decision analysis in engineering design appropriately. 4. There are activities in the design process that are decision activities but do not require the same type of decision-making as that used for selecting a final design -- which necessarily involves values, uncertainty, and risk assessment. Decision analysis could become too sophisticated or inapplicable for those activities. 5. The quantitative decision analysis will leave out many human and artistic qualities that engineering design possesses. The use of decision analysis in engineering

4. Ingenuity Choice Normative Decision Analysis Environment Uncertain Alternatives Complex Perception Probability - assignments Information Dynamic Outcome Decision Structure Logic Competitive e Value assessment Finite Preferences Time Preference Philosophy Risk Preference , Confusion, worry Think Praise, Blame Insight Act Joy sorrow Normative Decision Analysis in Decision-Making (Dr. Howard)

5. Excerpts from Ron Howard’s 1960s paper • Decision Analysis does not eliminate judgment, intuition, feelings, opinions, or anything like that. • Rather, it provides a mathematical framework to quantify them and express them in a form where logic can operate on them, rather than buried in human’s mind where we cannot get access to them.

6. Excerpts from Ron Howard’s 1960s paper • Can you obtain better outcomes by decision analysis that by following intuition? • “It is an act of faith.” A logical procedure based on sound principles you believe in is better than another approach. • When is it worthwhile to do decision analysis? • Do a “back-of-the-envelope” analysis: How much would it be worth more to do a more refined analysis? This itself can be treated as a decision and analyzed as such. • Decisions vs. Outcomes

7. Excerpts from Dr. Raiffa’s Lecture Notes (1960s) • “To make the correct engineering decisions requires extensive knowledge and experience in engineering. Mathematical ability alone will not suffice..” Admiral Rickover • Sprit of decision analysis is to divide and conquer • Decision Analysis requires explicit articulation of a though process • Everything is reduced to dollar signs and lives saved. What about the quality of life? • Decision Analysis conveniently features those aspects that are readily amenable to analysis and ignore like a plague intangibles that really count. What would you do otherwise?

8. Is Multiattribute Utility Analysis a useful method in Engineering Design? What is your approach to engineering decision making that involves multiple attributes and multiple decision makers?

9. Decision-making in Engineering Design • Decision: A choice from among a set of alternatives, an irrevocable allocation of resources • Options • Expectations • Outcome under Uncertainty: Process, Model, Computational • Preferences & utility • Possibly Continuous Alternatives and Limitless design options • Options May be Unknown a-priori • Heavy reliance on Simulation and Computational Models

10. Decision-based Design • Generation of option/design space • Exploration/Formulation of option space • Computation of outcome expectation resulting from the choice of a particular option • Establishment of a value system to rank the expectations

11. Expected Utility • Optimal solution rule (Preferred Option) • obtaining the highest overall Expected Utility value • Need to develop the preference structure and utility functions • Consistent with vN-M Axioms • “Mathematical techniques that attempt to construct the preference order by directly eliciting the decision makers preferences..” • Bottom Line: • Correct Preference Correct Utility Correct Decision • Utility Theory: Mathematically rigorous approach to expressing human preferences • MAU: Keeney & Raiffa, von Winterfeldt & Edwards, others • MAU in Engineering Design: Thurston, Krishnamurty, others

12. What are the top research issues for developing DBD approaches to design?

13. Quality will decide: • Common sense, good judgment, experimental & knowledge based, Probability & Statistics, utility theory, validation (Bayesian), etc. • Equally important: • Attending DBD workshops, Gordon Conferences • Organizing Special Editions in Journals & Sessions in Conferences • Serving on NSF Panels Be supportive!!