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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

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Session Agenda Evaluating

Alternatives 40 min Working on Project

(review of somenotebook work) 35 min

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Learning Objective

Achieve awareness of the differences between Relative Ratings and Absolute Ratings in completing Scoring Tables (Matrices)

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Sample Scoring Table

Cri

teri

a W

eigh

ts

Concept 1

Concept 2

Concept 3

Criteria ACriteria BCriteria C

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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

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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

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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

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The Weighted Objectives Method [1]

List Design Objectives Rank-order the list Assign Relative weights to

objectives Establish performance parameters

or utility scores for each objective Calculate relative utility values for

alternatives

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Reference for Today’s Material

[1] N. Cross, “Evaluating Alternatives,” in Engineering Design Methods, Chichester, John Wiley and Sons, 1989, pp. 101-121.

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1. List Design Objectives Decision requires criteria

(objectives) Includes:– Technical factors– Economic factors– User requirements– Safety requirements– Etc.

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2. Rank-order Objectives

Individual: Ordered set of note cards to indicate relative importance

Team: pair wise comparison matrix or table

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Pairwise Comparison

A B C

A

B

C

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Pairwise Comparison

A B C

A 1

B 0

C

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Pairwise Comparison

A B C

A 1 1

B 0

C 0

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Pairwise Comparison

A B C

A 1 1

B 0 1

C 0 0

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2. Rank-ordering continued

Order established The ordering is an ordinal

scale Ordinal scales should not be

used in arithmetical operations

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3. Assign Relative Weightings to Objectives

Use rank ordering to spread out along a 1 to 10 scale

Assign a fixed number of points, say 100) among the objectives

Utilize an Objectives Tree

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Example Objectives Tree

G1

1.0 1.0

G11

0.5 0.5

G12

.25 .25

G13

.25 .25

ManufacturingCost

AestheticallyPleasing

LongLasting

G111

0.6 0.3

G112

0.4 0.2Cost of Materials

Cost of Assembly

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3. Assign Relative Weightings Continued

The relative weightings are an interval value scale

Interval value scales can be used in arithmetic operations

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4. Establish Utility Scores for Objectives

Need to convert objectives into things measured (metrics)

Establish a scale to define what is good; what is bad

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Two Sample Scales11 Pt Scale Meaning 5 Pt Scale Meaning

0 Total useless 0 Inadequate1 Inadequate

2 Very poor 1 Weak3 Poor

4 Tolerable

5 Adequate 2 Satisfactory6 Satisfactory

7 Good 3 Good8 Very good

9 Excellent 4 Excellent10 Perfect

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Scale for Car ObjectivesScale Fuel Consumption

(miles/gal)Comfort

0 <27 Very uncomfortable

1 29 Poor Comfort

2 32 Below Average Comfort

3 35 Average Comfort

4 38 Above Average Comfort

5 41 Good Comfort

6 >43 Extremely Comfortable

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Figure 1 - Linear Mapping of Mass Into Rating

0

1

2

3

4

5

0 20 40 60 80 100 120 140mass (g)

Rat

ing

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Figure 2 Non-linear Mapping of Mass Into Rating

0

1

2

3

4

5

0 20 40 60 80 100 120 140mass(g)

Rat

ing

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Figure 3 Non-linear Mapping of Mass Into Rating

0

1

2

3

4

5

0 20 40 60 80 100 120 140mass(g)

Rat

ing

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Calculate Relative Utility Values for Alternatives

Review Figure 62 on handout Notice untility scores for each

concept fragment and each objective (upper left corner, see Notes for meaning)

Which concept(s) is the winner?

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Comments on Notebook Assessment

None of the Notebooks received at least a Meets for TA5 even though there was evidence of much work being done

Most assessments for IA8 were meets but there were some E’s and a few NI’s

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Notebook Assessment Continued

The notebook work (TA5 & IA8) is the one body of work that can be reassessed as M or E independent of the first assessment

I will log in the best assessment received for TA5 and IA8