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Indicate whether the statement is true or false.
1. Keeping special cause variation from occurring is the essence of statistical quality control.
a. True
b. False
2. The 1:10:100 Rule states that if a defect is first detected during the production process, it might cost $1 to fix.
a. True
b. False
3. In the context of quality control practices in manufacturing, if supplier documentation is done properly, incoming
inspection can be completely eliminated.
a. True
b. False
4. In-process control is typically performed by people who run the back-end processes.
a. True
b. False
5. Overadjusting a process that is in control will decrease the variation in the output.
a. True
b. False
6. The control limits represent the range between which all points are expected to fall if the process is in statistical control.
a. True
b. False
7. A discrete metric is one that is calculated from data that are counted.
a. True
b. False
8. The value of the process capability index, (Cp), depends on the mean of the process.
a. True
b. False
9. Designing control charts involves two key issues: sample size and sampling frequency.
a. True
b. False
Indicate the answer choice that best completes the statement or answers the question.
10. Which of the following is not one of the components of a control system?
a. A performance standard or goal
b. A means of measuring actual performance
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c. Customer feedback forms and the service people who process and address them
d. Comparison of actual performance with the standard to form the basis for corrective action
11. The task of _____ is to ensure that a good or service conforms to specifications and meets customer requirements by
monitoring and measuring processes and making any necessary adjustments to maintain a specified level of performance.
a. job design
b. visual control
c. quality control
d. forecasting
12. In determining whether a process is in statistical control, the _____ is always analyzed first.
a. R-chart
b. p-chart
c. x
̄–chart
d. c-chart
13. If a process has a process capability index value (Cp) of less than 1, it means that:
a. a significant percentage of output will not conform to the design specifications.
b. both the lower and upper specification limits are met.
c. the observed variation is the same as the design specification width.
d. the process is very capable of meeting the upper specification limit.
14. A bottling machine fills soda bottles with an average of 12.000 ounces of soda. The standard deviation is 0.002
ounces. If the design specification for the fill weight of the bottles is 12.000 ounces plus or minus 0.015 ounces, calculate
the process capability index of the machine.
a. Less than or equal to 1
b. More than 1 but less than or equal to 2
c. More than 2 but less than or equal to 3
d. More than 4
15. In the context of the net promoter score (NPS), which of the following is a difference between promoters and
detractors?
a. Unlike promoters, detractors are customers who are associated with scores of 7 or 8.
b. Unlike promoters, detractors are satisfied customers who may switch to competitors.
c. Unlike promoters, detractors defect at higher rates.
d. Unlike promoters, detractors are less price sensitive.
16. When the _____ is extremely low, standard control charts are not effective.
a. efficiency rate
b. demand flow
c. rate of defects
d. perceived value
17. A hotel chain periodically analyzes its service times to check for variation in service processes. To do this, it uses R-
charts. Seven samples, each containing observed checkout time with three different customers, were collected. The
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average mean and the average range of the service times are found to be 9.924 and 0.957, respectively. If D4 for the R-
chart is 1.924, the upper control limit (UCLR) for the R-chart will be:
a. less than or equal to 1.0.
b. greater than 1.0 but less than or equal to 1.5.
c. greater than 1.5 but less than or equal to 2.0.
d. greater than 2.0 but less than or equal to 2.5.
18. The lower and upper specification limits for a toothpaste filling machine are 10.50 and 12.00 ounces, respectively. The
standard deviation is 0.05. The process capability index of the machine will be:
a. less than or equal to 3.
b. more than 3 but less than or equal to 5.
c. more than 4 but less than or equal to 5.
d. more than 5.
19. Ratterman and Son, is a custom landscaping company. Data in the table below show results for the question “Would
you recommend us to a friend?” from 50 customers who were sampled over the duration of one week.
Customer Number NPS Rating Customer Number NPS Rating Customer
Number NPS Rating Customer Number NPS Rating Customer Number NPS Rating
1 6 11 8 21 4 31 1 41 8
2 9 12 9 22 9 32 9 42 9
3 10 13 7 23 9 33 3 43 9
4 9 14 4 24 10 34 9 44 9
5 5 15 1 25 9 35 9 45 2
6 10 16 3 26 10 36 7 46 5
7 6 17 7 27 5 37 4 47 9
8 9 18 6 28 10 38 10 48 10
9 4 19 5 29 10 39 9 49 9
10 7 20 10 30 6 40 5 50 8
Calculate the net promoter score.
a. 14%
b. 17%
c. 24%
d. 27%
20. In the context of statistical process control and variation, if no special causes affect the output of a process, we say that
the process is _____.
a. inconsistent
b. out of control
c. in control
d. overadjusted
21. In the context of the net promoter score (NPS), scores of 6 or below represent _____, unhappy customers who may
spread negative comments.
a. detractors
b. passives
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d. campaigners
22. In the context of designing control charts, which of the following is true of a sample size?
a. A large sample allows small changes in process characteristics to be detected with higher probability than a small
sample size.
b. A small sample is used to detect process shifts of two standard deviations or smaller.
c. A large sample size is desirable to keep the cost associated with sampling low.
d. A small sample size provides greater degrees of statistical accuracy in estimating the true state of control than a
large sample size.
23. An operator wants to determine the standard deviation for a machine she operates. To do this, she wants to create a p-
chart. Over a month’s time, she collects 30 samples of 75 observations each and records the number of errors. The average
proportion defective is found to be 0.024. Which of the following is the standard deviation (s) of the machine?
a. Less than or equal to 0.1
b. More than 0.1 but less than or equal to 0.5
c. More than 0.5 but less than or equal to 1.0
d. More than 1.0
24. Which of the following is true of control charts?
a. Control charts can only be used for processes that have a very high sigma level.
b. The use of small sample sizes in control charts increases the chances that a process may have changed during the
sampling interval.
c. Conventional statistical process control charts have the lowest frequency of false alarms.
d. Standard control charts are not effective when the rate of defects is extremely low.
25. Which of the following is the upper control limit for a c-chart (UCLc) with the average number of nonconformances
per unit equal to 7?
a. More than 11 but less than or equal to 12
b. More than 12 but less than or equal to 13
c. More than 13 but less than or equal to 14
d. More than 14 but less than or equal to 15
26. The time taken for guests to check out at a hotel front desk was measured over the course of several weeks. The
management believes that the target time for checking out guests should be between 2 and 3 minutes with a target of 2.5
minutes. The data gathered for the actual process had a mean time of 2.75 minutes with a standard deviation of 0.45
minutes. The process capability index will be:
a. less than or equal to 1.
b. more than 3 but less than or equal to 5.
c. more than 4 but less than or equal to 5.
d. more than 5.
27. Customer waiting time and order lead time are examples of _____ metrics.
a. discrete
b. countable
c. isolated
d. continuous
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28. In the context of the net promoter score (NPS), scores of 7 or 8 are associated with _____, customers who are satisfied
but may switch to competitors.
a. detractors
b. passives
c. promoters
d. proponents
29. The relationship between the natural variation and specifications is quantified by a measure known as the _____.
a. net promoter score
b. process capability index
c. net detractor score
d. process design index
30. A process capability study is designed to yield specific information about _____.
a. the effect of changing one aspect of a system at a time
b. the rate of decay of a system as the equipment ages and begins to fail
c. the performance of a process under specified operating systems
d. how introducing multiple variances in the system at once affect the outcome of a process
31. Which of the following is the upper control limit for a c-chart (UCLc) with the average number of nonconformances
per unit equal to 7?
a. More than 11 but less than or equal to 12
b. More than 12 but less than or equal to 13
c. More than 13 but less than or equal to 14
d. More than 14 but less than or equal to 15
32. Vincent, a quality control manager at an apparel manufacturing company, studies and monitors quality using R-charts.
He discovers a quality problem with the construction of zippers. Vincent proposes that 25 samples of eight observations
each be collected on a daily basis. He plans to prepare an R–chart to monitor the variation in the size of the zippers. The
data collected shows that the mean length of the zippers is 15 inches and the average range is 0.5 inches. If D3 for the R–
chart is 0.136, the lower control limit (LCLR) for the R–chart will be:
a. less than or equal to 1.
b. more than 1 but less than or equal to 2.
c. more than 2 but less than or equal to 3.
d. more than 4.
33. Which of the following is true of common cause variation?
a. It can be controlled and described using nonstatistical methods.
b. It appears at random, and individual sources cannot be identified or explained.
c. It accounts for about 10 to 15 percent of the observed variation in a process.
d. It arises from external sources that are not inherent in a process.
34. Which of the following is true of special cause variation?
a. It cannot be explained or understood.
b. It occurs sporadically and can be prevented.
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c. It cannot be detected using statistical methods.
d. It accounts for about 80 to 95 percent of the observed variation in a process.
35. Quality at the _____ means that the people responsible for the work control of their processes by identifying and
correcting any defects or errors when the first are recognized or occur.
a. conclusion
b. workstation
c. source
d. delivery
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Answer Key
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