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As Class Convenes. Find your team Sign attendance form Insert any work due today and Return folder to the front desk. Session Agenda. Getting Started 5 min Using Relative 15 min Ranking in Scoring Tables Using Absolute 30 min Ratings in Scoring Tables . Learning Objective.
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As Class Convenes • Find your team • Sign attendance form • Insert any work due today and • Return folder to the front desk
Session Agenda • Getting Started 5 min • UsingRelative15 minRanking in Scoring Tables • UsingAbsolute30 minRatings in Scoring Tables
Learning Objective Achieve awareness of the differences between RelativeRatings and AbsoluteRatings in completing Scoring Tables (Matrices)
Session Agenda • Getting Started 5 min • UsingRelative15 minRating in Scoring Tables • Using Absolute 30 min Ratings in Scoring Tables
Determining Ratings: The Text Book Says • Use relative comparisons • Use a simple rating scale 1 = much worse than reference to 5 = much better than reference
Problems With Relative Rating • Scale Compression • if reference concept is the best relative to criterion 1, what rating values are available for criterion 1? • only 1 (much worse), 2 (worse) & maybe 3 (same) • Not rigorous for non experts
In Some Cases We Can Do Better • Use absolute instead of relative rating of concepts • Use engineering science to predict the values of the criteria for the concepts
A Class Exercise For a two criteria, three “concepts” problem, you will evaluate the “concepts” • using relative rating • using absolute values with mapping to a rating
The Problem NASA wants to launch another probe to Mars. This probe requires a widget that TeamUSA has agreed to design and make. NASA wants a low mass, low costwidget. Three feasible concepts have been created; which one should be selected?
Three Widget Concepts • anABS plasticcube4.8 cm on a side, $2000 • a Bakeliterod 5.0 cm long & 2.5 cm in diameter, $4000 • a glassrod 5.0 cm long & 2.8 cm in diameter, $6000
Relative Rating Scale • Much Worse • Worse • About the Same • Better • Much Better light isbetterthan heavy
Rate Concepts Using Relative Comparison Method Using Concept C as the reference, rate Concepts A & B 3 1 4
Session Agenda • Getting Started 5 min • Using Relative 15 min Ranking in Scoring Tables • UsingAbsolute30 minRatings in Scoring Tables
Using Absolute Ratings • Evaluate the criterion for each concept, i.e., calculate the mass of each concept
Using Absolute Ratings • Why can't you use the calculated mass directly in the Scoring Table? • You can change the results in the table by just changing the units (metric tons vs micro grams)
Using Absolute Ratings (cont’d) • You needto map the calculated masses into a dimensionless 1 to 5 rating scale • What is a map? A map is a function that converts one value (e.g., a criterion value) into another value (e.g., a rating)
112 37 80 Rate The Concepts Using Absolute Comparison Method Using your team’s map, rank Concepts A, B, & C
Summary of Mapping Results 2 4.5 3 1.1 2 1.6 4 4.8 4.2
Analysis of Scoring Tables • Does the mapping change the relative rankings? no, A is always the worst and B is always the best • What does change with different mappings? the value in the table, A ranges from 1 to 4
