Welcome W 6.1 Introduction to Engineering Design II (IE 202) Chapter 3: Measuring Things 1 1

Today’s Learning Outcomes By the completion of today's meeting, students should be able to: Be able to rank the client’s objectives. Establish assessment scales for measuring success in achieving objectives. 2 2

Preview What have we covered so far? Overall Design Process Project Management Problem Definition (Identifying Client’s Objectives) 3 3

1st Task in the Design Process 4 4

What’s Next? Having defined the client’s objectives How do we know it had been achieved? Measurement scales Are there any priorities among them? Setting weights 5 5

Measurement Basics Defined reference (e.g. zero) Units (e.g. oC, m, kg, sec.) These enable strong measurement. 6 6

Design scales are usually Subjective. Nominal scales; for differentiation Partially ordered scales; father & son Ordinal scales; 1st, 2nd, 3rd, … Ratio scales; cm, sec., $, … Interval scales; oC Multidimensional scales; km/hr Design scales are usually Subjective. 7 7

Creativity Break How can cut these cakes into 3 equivalent parts? 8 8

Setting Priorities Are all objectives of the same importance to the client? Is it an important issue? The basic measurement scheme: more/less – better/worse The Golden Rule: Don’t mix apples with oranges, compare apples with apples and oranges with ora. 9 9

Pairwise Comparison Chart PCC is a table constructed to evaluate the objectives. It is a simple straightforward rank ordering scale. Each team member constructs his own table. The overall weight is found by simple averaging. Team consensus may be used instead. Arrow Impossibility decision theorem by K. J. Arrow (1972) => Noble Prize in eco. 10 10

Juice Container for the Kids a sheet of paper and hand As teams: Is it OK to ignore the one with 0 score? Explain why? Example Using PCC Juice Container for the Kids Write your answers in a sheet of paper and hand it to your instructor. As teams: What is the criterion, the row cell or the column cell? Explain why. 11 11

Note: PCC is not Weighted ranking PCC Aggregate Ordering What if we have a team of designers? Suppose this is the result of 12 votes:  A > B > C  B > C > A A > C > B  C > B > A What is the result of the vote? C > B > A Note: PCC is not Weighted ranking 12 12

Metrics How can one measure achievements? What if your doctor said Your eye pressure is 15?! What should you answer? What is the ideal? Metrics How can one measure achievements? Metric: actually measure the objective. Appropriate units & Correct scale, e.g. Ladder weight: cm kg Tons mg SR sec. ? Next, assign points, e.g. 50 – 200 km/hr 0 point: 50 km/hr, 100 points: 200 km/hr Cellphone Durability: drop tests of 1-3 m      13 13

Measurement Plan There must be a measurement plan: Direct/calculated measurement Estimated measurement Consumer surveys But, may not be available until … Popular scales: high/medium/low or str.agree/agree/notdec/disagree/str.disagr Do you know of a similar system? Your grades! Likert Scale 1, 2, 3, 4 & 5 German VDI 2225 0, 1, 2, 3 & 4 Use-Value Analysis 0: absolutely useless 10: ideal, How many? 14 14

Remarks on Metric Assess. All assessment has to be done consistently on the same scale. A metric should be repeatable Outcomes should be expressed in understandable units of measure. The results should lead all parties involved in the design process to the same conclusion. 15 15