15) Floyd Electric is fabricating flanges for a new electrical motor. The flange is to be 25 millimeters in
diameter with an upper tolerance limit of 26.5 millimeters and a lower tolerance limit of 23.5 millimeters.
Bill Floyd took a sample consisting of ten flanges, measured the diameter and recorded the observations
in the table. He has heard discussion of 6 sigma in the business news recently and would like to join the
club.
25.69
25.58
24.78
24.94
24.87
24.63
25.70
25.52
24.95
24.91
What percentage decrease in process standard deviation would be required for Floyd Electric to achieve
6-sigma process capability? Assume that his process mean remains where it is.
A) 36%
B) 40%
C) 46%
D) 58%
16) A housekeeping supervisor inspects rooms after the staff has cleaned them and compares their staff’s
performance against a checklist of items that should be cleaned, replaced, etc., according to standard
operating procedure at the hotel. Over the past week she finds three rooms that have cleaning mistakes
out of the 140 rooms she has inspected. How many additional rooms should she sample to establish an
average fraction defective for the p chart she would like to make to monitor this process?
A) 78
B) 93
C) 108
D) 133
17) The probability of rejecting a lot with quality better than the acceptable quality level is:
A) the lot tolerance percent defective.
B) the lot tolerance percent acceptable.
C) the consumer’s risk.
D) the producer’s risk.
18) Taguchi defines quality in terms of:
A) parts per million.
B) losses.
C) lot tolerance percent defective.
D) acceptable quality levels.
19) What does the traditional quality loss function look like?
A) a parabola
B) a line with slope=1
C) a goalpost
D) a hyperbola
20) What does the Taguchi quality loss function look like?
A) a parabola
B) a line with slope=1
C) a step function
D) a hyperbola
21) Taguchi’s quality loss function is consistent with:
A) employee empowerment.
B) ISO 9000
C) quality function deployment.
D) the total costs of quality.
22) A reduction in process variance results in a higher process capability.
23) Six Sigma quality means that the difference between the upper and lower tolerance levels is six
standard deviations wide.
24) If a contact lens has a scratch on it, the manufacturer classifies it as defective. This is an example of a
continuous variable.
25) The width between the upper and lower limits of a control chart should be wider than the width
between the upper and lower tolerance limits.
26) An R chart is used to track how much the individual observations within a sample vary.
27) In general, producer’s risk rises as consumer’s risk falls.
28) With everything else held constant, a sampling plan with c = 1 will have a lower producer’s risk than a
sampling plan with c = 2.
29) Taguchi’s quality loss function runs counter to the notion that a product falling within tolerance limits
is acceptable.
30) The ability of a non-centered process to meet certain tolerance limits is measured by its ________.
31) ________ measures refer to the presence or absence of a particular characteristic.
32) The probability of accepting a lot with worse quality than the lot tolerance percent defective level is
________.
18
33) Taguchi’s ________ demonstrates that as soon as a quality characteristic deviates from the target
value, there is a decline in the level of quality.
34) An airline wants to monitor the performance of their baggage handling crew on the daily flight from
Oklahoma City to Dallas that is always filled to its 140 passenger capacity. They track the number of
passengers that lose bags each flight for a two-week period. The data are displayed in the following table.
Determine control limits for the appropriate chart and indicate any points that are out of control.
Day #
# Bags Lost
1
3
2
4
3
3
4
2
5
5
6
7
7
6
8
8
9
1
10
7
11
6
12
2
13
1
14
7
19
Copyright © 2019 Pearson Education, Inc.
Answer: This is attribute data, so a p-chart is called for. The upper and lower control limits are 0.076 and
0 and all samples fall comfortably within this range.
= =
=
= (0.0316)
Sp =
=
= 0.0148
UCL = + 3Sp LCL = – 3Sp
UCL = 0.0316 + 3(0.0148) LCL = 0.0316 – 3(0.0148)
UCL = 0.076 LCL = -0.013 ∴ LCL = 0
Day #
# Bags Lost
1
3
2
4
3
3
4
2
5
5
6
7
7
6
8
8
9
1
10
7
11
6
12
2
13
1
14
7
20
Copyright © 2019 Pearson Education, Inc.
35) A hot tub manufacturer wants the thermostat to control water temperature to within one degree when
set at 130 degrees Fahrenheit. They randomly select 10 hot tubs, set the thermostats to 130, and record the
following data with an infrared thermometer that has recently been calibrated.
Temp
129.9
129.7
130.2
129.7
129.8
130
129.6
131
130.3
129.8
What is their process capability?
21
Copyright © 2019 Pearson Education, Inc.
Cp =
Cp = 0.80
Their process capability is poor.
Diff: 3
Reference: 5.4 Statistical Quality Control
Keywords: process capability ratio, standard deviation, Cp
AACSB: Analytical Thinking
LO: 5.4: Calculate process capability ratios and indices and set up control charts for monitoring continuous variables
and attributes.
36) Floyd Electric is fabricating flanges for a new electrical motor. The flange is to be 25 millimeters in
diameter with an upper tolerance limit of 26.5 millimeters and a lower tolerance limit of 23.5 millimeters.
Bill Floyd took a sample consisting of ten flanges, measured the diameter and recorded the observations
in the table.
25.69
25.58
24.78
24.94
24.87
24.63
25.70
25.52
24.95
24.91
What is Floyd Electric’s process capability?
37) The fill size for a small bag of peanuts distributed by a popular airline is 50 grams. The producer
wishes to set up a set of control charts for this process and collects the data shown in the table. Develop
the proper statistical quality control charts. Is the process in control?
Sample
Item #1
Item #2
Item #3
Item #4
Sum
1
54.5
54.3
53.8
50.4
213.00
2
50.6
53.5
53.2
54.9
212.20
3
51.1
54.3
50.4
50.7
206.50
4
52.7
52.1
51.3
51.0
207.10
5
51.7
51.2
54.7
54.3
211.90
6
51.1
51.5
54.7
50.4
207.70
7
54.0
52.3
54.7
51.4
212.40
8
53.2
50.4
53.4
51.4
208.40
9
51.9
50.2
50.2
52.9
205.20
1
4.1
2
4.3
3
3.9
4
1.7
5
3.5
6
4.3
7
3.3
8
3.0
38) A cell phone manufacturer inspects the video display on each color phone to verify that the screen can
display all colors with the brilliance their customers have come to expect. Each phone is turned on, run
through a self-test procedure, and classified as either acceptable or unacceptable based on test
performance. The production team takes a sample of 350 phones and finds one with a defective display.
How many additional phones should they sample to establish an average fraction defective for their
statistical quality control initiative?
39) What are the advantages of acceptance sampling over 100% inspection?
40) What is the shape of the ideal OC curve? Explain the key elements of the curve
41) A tailor decides to use Taguchi’s quality loss function to analyze his shirt making process. Knowing it
to be parabolic in shape and of the form L(y) = k(y – t)2 where t is the target, y is the actual measurement,
and k is the process constant, the tailor decides to use a recent customer order to calculate his process
parameters. He takes the custom shirt and measures the collar, which was requested to have a 17.5″ collar
but actually has a 17.75″ collar. The customer notices the difference and demands a 50% reduction in the
price of the shirt, which cost the tailor $45 to make. Instead of selling the shirt for $175, the tailor will
reduce his price to $87.50. What is the tailor’s process constant for a silk shirt?
42) Describe the Taguchi quality loss function. What is its shape and what are the implications of this
curve?
5.5 Managing Quality Across the Supply Chain
1) One international standard for managing quality across the supply chain is:
A) ISO 9000.
B) ISO 14000.
C) AQL.
D) LTPD.
2) ISO 9001:2015 can be used by both manufacturing and service companies.
3) ________ is a family of standards, supported by the International Organization for Standardization,
representing an international consensus on good quality management practices.
4) Describe the ISO 9000 family of standards, including the objectives and process of becoming certified.