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Multiple Choice Questions on Chapter 15: Robust Design 1. Robust design is the product development activity of ____________ the desired performance of the product while ___________ the effects of noise. a) improving; ignoring b) improving; minimizing c) ignoring; improving d) ignoring; minimizing Answer: B 2. According to the text book, ____________ and ______________ are used to identify robust setpoints for the design parameters which can be controlled. a) theoretical models; cost analysis b) theoretical models; data analysis c) experiments; data analysis d) experiments; cost analysis Answer: C

Figure 15-1: Example of the effects of design parameters, Factor A (linear) and Factor B (Non-linear) on overall performance of a product 3. To perform robust design i.e., minimizing the effect of variation for the product shown in Figure 15-1 the development team decided that: a) Choosing A1 minimizes the effect of variation in factor A on overall performance b) Choosing A2 minimizes the effect of variation in factor A on overall performance 15-1

c) Choosing B1 minimizes the effect of variation in factor B on overall performance d) Choosing B2 minimizes the effect of variation in factor B on overall performance Answer: C 4. Although it is beneficial to consider product robustness as early as the concept stage, experiments for robust design are used most frequently during the _________ phase. a) system level design b) detail design c) production d) at any development Answer: B 5. As per the text book, the Design of Experiment (DOE) method for robust design includes the use of a signal-to noise ratio metric to observe the ___________ performance (signal) and ____________ effects (noise). a) desired; undesired b) undesired; desired c) desired; desired d) undesired; undesired Answer: A 6. A ______________ step process is prescribed in the text book in order to develop a robust product. a) four b) five c) six d) seven Answer: D 7. As described in the text book, the first step to develop a robust product is to: a) develop the experimental plan. b) conduct the analysis. c) identify control factor, noise factor, and performance metrics. d) select and confirm factor setpoints. Answer: C 8. For the robust design of the seat-belt example from the text book, the “Belt webbing stiffness” was one of the _______ factors 15-2

a) b) c) d)

noise control performance metrics signal Answer: B

9. For the robust design of the seat-belt example from the text book, the “shape of the seat” was one of the _________ factors. a) noise b) cost c) control d) performance metrics Answer: A 10. For the robust design of the seat-belt example from the text book, the “back angle” was one of the: a) signal factors b) noise factors c) control factors d) performance metrics Answer: D 11. For the robust design of the seat-belt example from the text book, the primary concern was the effect of three particular noise factors; they were: a) seat shape; wear of components; size of passenger b) type of fabric; positioning of passenger; type of seat fabric c) wear of components; size of passenger; severity of collision d) seat shape; fabric type; severity of collision Answer: D 12. As described in the text book, common forms of maximizing an objective function η is: a)

η=µ or η = µ 2

b) c)

η=σ2

d) where,

η is the objective function 15-3

µ is the mean of the experimental observations under a given test condition. σ is the variance of the experimental observations under a given test condition. t is the target value. Answer: A 13. As described in the text book, common forms of minimizing an objective function η is a)

η=µ2

b) c)

η=µ or η = σ 2

d) where,

η is the objective function µ is the mean of the experimental observations under a given test condition. σ is the variance of the experimental observations under a given test condition. t is the target value. Answer: C 14. One of the common forms of reaching a target value for an objective function is a) b) c) d) where,

η is the objective function µ is the mean of the experimental observations under a given test condition. σ is the variance of the experimental observations under a given test condition. t is the target value. Answer: B 15. As per the text book, a common maximizing form of the objective function, signal-to noise ratio is a) b) 15-4

c) d) where,

η is the objective function µ is the mean of the experimental observations under a given test condition. σ is the variance of the experimental observations under a given test condition. t is the target value. Answer: D 16. For the robust design example of seat-belt experiment, Ford development team suggested that the two objective functions, the average back angle at peak to be ____________, and the range of the back angle at peak to be ___________. a) minimized; maximized b) minimized; minimized c) maximized; minimized d) maximized; maximized. Answer: B 17. A full factorial experimental design involves: a) the systematic exploration of every combination of levels of each factor b) use of only a small fraction of the combinations of levels of each factor c) use of the smallest fractional factorial plan that still allows the team to identify the main effects of each factor d) an unbalanced experimental plan where each trial is conducted with all but one of the factors at nominal levels Answer: A 18. Experimental design may use orthogonal array design, which involves: a) systematic exploration of every combination of levels of each factor b) use of the smallest fractional factorial plan that still allows the team to identify the main effects of each factor c) use of only a small fraction of the combination of levels of each factor d) an unbalanced experimental plan where each trial is conducted with all but one of the factors at nominal levels Answer: B 19. One factor at a time type of experimental design involves: 15-5

a) systematic exploration of every combination of levels of each factor b) use of the smallest fractional factorial plan that still allows the team to identify the main effects of each factor c) an unbalanced experimental plan where each trial is conducted with all but one of the factors at nominal levels d) use of only a small fraction of the combination of levels of each factor Answer: C 20. The fractional factorial type of experimental design involves: a) systematic exploration of every combination of levels of each factor b) use of the smallest fractional factorial plan that still allows the team to identify the main effects of each factor c) an unbalanced experimental plan where each trial is conducted with all but one of the factors at nominal levels d) use of only a small fraction of the combination of levels of each factor Answer: D 21. Which one of the following is not one of the common ways to test noise factors? a) assign additional columns in the orthogonal array of fractional factorial layout to the noise factor b) use an outer ray for the noise factor c) run replicates of each row, allowing the noise to vary in a natural uncontrolled manner throughout the experiment d) run replicates of each row with correlated noise Answer: D 22. As described in the text book, running replicates of each row with compounded noise is a way to measure: a) control factors b) noise factors c) performance metrics d) signal factors Answer: B 23. The Ford team chose to utilize the ______________ approach in the seat-belt experiment. a) use of an outer array for the noise factor b) method of running replicates of each row 15-6

c) compounded noise d) assignment of additional columns in the orthogonal array Answer: C 24. The analysis of means involves_________ all the computed objective functions for each factor level. a) adding b) averaging c) correlating d) finding variances for Answer: B 25. To achieve robust performance, use of objective functions helps in capturing: a) mean performance of each control factor b) variance of performance due to noise factors c) both a) and b) d) neither a) or b) Answer: C

Figure 15-2: Factor effects charts for Back Angle for the seatbelt experiment from Ford Company 26. In Figure 15-2 shown above _____________ appears to have no effect upon mean performance. a) Factor B b) Factor C 15-7

c) Factor D d) Factor E Answer: C

Figure 15-3: Factor effects charts for Back Angle for the seatbelt experiment from Ford Company 27. Figure 15-3 suggests that levels __________ will minimize the range of Back Angle at peak. a) A1, B2, C2, D1, E1, F1, G2 b) A1, B2, C2, D1, E1,F1,G1 c) A2, B2, C2, D1, E1, F2,G1 d) A2, B2, C2, D2, E2, F1, G2 Answer: C

Figure 15-4: Example of an Orthogonal Array for 3 factors at 2 levels each 28. The factor levels missing in the Figure 15-4 shown above are 15-8

a) b) c) d)

1, 2, 3 2, 1, 3 1, 1, 2 2, 1, 2 Answer:

29. One of the basic assumptions made in interpreting analysis of means is that the : a) factor effects are independent, without interactions across the factors b) factor effects are dependent on interactions across the factors c) interaction effects among the factors are included in the results d) interaction effects among the factors can’t be measured, hence ignored Answer: A 30. Interaction effects across the factors can be explored by a) executing a larger fractional factorial design. b) using an adaptive one-at-a time experimental plan. c) assigning specific interactions to be explored in certain columns of the orthogonal array. d) all of the above. Answer: D

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