Deck 14: Statistical Process Control

Question 1

Construct an R chart and determine whether the process variation is within statistical control. A machine is supposed to fill cans that contain 12 ounces. Each hour, a sample of four cans is tested; the results of 15
consecutive hours are given below.

Answer 1

Question 2

A common goal of quality control is to reduce variation in a product or service. List and describe the two types
of variability. Give an example of each.

Answer 2

Random variation is due to chance, the variation inherent in any process that is not capable of producing
each good or service exactly the same way every time. Assignable variation results from causes that can
be identified. Examples may vary.

Question 3

Construct an R chart and determine whether the process variation is within statistical control. A machine that is supposed to fill small bottles to contain 20 milliliters yields the following data from a test of 4 bottles
every hour.

Answer 3

The process appears to be within statistical control.

Question 4

Question 5

Define statistically stable (or "within statistical control"). Show examples of run charts which illustrate processes
which are not statistically controlled. Discuss the pattern which indicates the process is not statistically
controlled for each example.

Question 6

Examine the given run chart or control chart and determine whether the process is within statistical control. If it
is not, identify which of the three out-of-statistical-control criteria apply.

Question 7

A control chart for R is shown below. Determine whether the process variation is within statistical control. If it
is not, identify which of the three out-of-control criteria lead to rejection of statistically stable variation.

Question 8

Describe an R chart and give an example. What does it attempt to monitor?

Question 9

Sketch a control chart that indicates that a process is not statistically stable due to the run of 8 rule.

Question 10

Describe a run chart and give an example. Refer to the values on each of the axes as you describe the run chart.

Question 11

Are control charts based on actual behavior or on desired behavior? Give an example to illustrate the difference
between the two types of behavior.

Question 12

Use the given process data to construct a control chart for p. If the weight of cereal in a particular packet is less than
14 ounces, the packet is considered nonconforming. Each week, the manufacturer randomly selects 1,000 cereal packets
and determines the number that are nonconforming. The results for 12 consecutive weeks are shown below.

Question 13

Question 14

Examine the given run chart or control chart and determine whether the process is within statistical control. If it
is not, identify which of the three out-of-statistical-control criteria apply.

Question 15

Construct a run chart for individual values corresponding to the given data. A machine is supposed to fill boxes
to a weight of 50 pounds. Every 30 minutes a sample of four boxes is tested; the results are given below.

Question 16

Examine the given run chart or control chart and determine whether the process is within statistical control. If it
is not, identity which of the three out-of-statistical-control criteria apply. A run chart for individual values W is
shown below. Does there appear to be a pattern suggesting that the process is not within statistical control? If
so, describe the pattern.

Question 17

Use the given process data to construct a control chart for p. A manufacturer monitors the level of defects in the
television sets that it produces. Each week, 200 television sets are randomly selected and tested and the number of
defects is recorded. The results for 12 consecutive weeks are shown below.

Question 18

Describe the three criteria used to determine if a control chart indicates a process which is not statistically stable.

Question 19

A machine is supposed to fill boxes to a weight of 50 pounds. Every 30 minutes a sample of four boxes is tested; the
results are given below.

Question 20

Provide an appropriate response. Describe what process data are. Why are process data important to
businesses? What is a common goal of businesses using quality control?

Question 21

A control chart for attributes is to be constructed. Which process would have wider control limits, a process
which has been having a 5% rate of nonconforming items, or a process which has been having a 10% of
nonconforming items? Assume that both processes have the same sample sizes. For a given sample size, would
it be easier to detect a shift from 5% to 10% or a shift from 10% to 15%? Explain your reasoning.

Question 22

Examine the given run chart or control chart and determine whether the process is within statistical control. If it
is not, identify which of the three out-of-statistical-control criteria apply.

Question 23

Use the given process data to construct a control chart for p. A drugstore considers a wait of more than 5 minutes to
be a defect. Each week 100 customers are randomly selected and timed at the checkout line. The numbers of defects for
20 consecutive weeks are given below.

Question 24

Provide an appropriate response. A common goal of quality control is to reduce variation in a product or
service. List and describe the two types of variability. Give an example of each.

Question 25

A control chart for R is shown below. Determine whether the process variation is within statistical control. If it
is not, identify which of the three out-of-control criteria lead to rejection of statistically stable variation.

Question 26

Question 27

Sketch a run chart that that indicates that a process is not statistically stable due to increasing variation.

Question 28

Describe the three criteria used to determine if a control chart indicates a process which is not statistically stable.

Question 29

Construct an R chart and determine whether the process variation is within statistical control. A machine that is supposed to produce ball bearings with a diameter of 7 millimeters yields the following data from a
test of 5 ball bearings every 20 minutes.

Question 30

Construct a run chart for individual values corresponding to the given data. A machine that is supposed to
produce ball bearings with a diameter of 7 millimeters yields the following data from a test of 5 ball bearings
every 20 minutes.

Question 31

Control charts are used to monitor changing characteristics of data over ________.

A) time
B) speed
C) distance
D) space

Question 32

Construct an chart and determine whether the process variation is within statistical control. A machine that is supposed to produce ball bearings with a diameter of 7 millimeters yields the following data
from a test of 5 ball bearings every 20 minutes.

Question 33

A run chart for individual values is shown below. Does there appear to be a pattern suggesting that the process
is not within statistical control? If so, describe the pattern.

Question 34

Define statistically stable (or "within statistical control"). Show examples of run charts which illustrate processes
which are not statistically controlled. Discuss the pattern which indicates the process is not statistically
controlled for each example.

Question 35

Question 36

A control chart for s shown below. Determine whether the process mean is within statistical control. If it is
not, identify which of the three out-of-control criteria lead to rejection of a statistically stable mean.

Question 37

Describe a p chart and give an example. What does it attempt to monitor?

Question 38

________ data are data arranged according to some sequence. They are a measurement of a characteristic or good or services that result from some combination of equipment, people, materials, methods, and conditions.

A) Process
B) Service
C) Material
D) Sequential

Question 39

Examine the given run chart or control chart and determine whether the process is within statistical control. If it
is not, identify which of the three out-of-statistical-control criteria apply.

Question 40

Which of the following is not one of the criteria for determining if a control chart indicates that a process is not statistically stable?

A) Decreasing variation
B) Downward trend
C) Upward shift
D) Exceptional value

Question 41

Examine the given run chart or control chart and determine whether the process is within statistical control.

A) The process is within statistical control.
B) The process is not within statistical control.

Question 42

Which type of chart does not have control limits?

A) x chart
B) p chart
C) R chart
D) Run chart

Question 43

The centerline for a control chart for R consists of ________.

A) the median
B) the mean of the sample data
C) the standard deviation
D) the mean of the sample ranges

Question 44

R charts are used to monitor ________.

A) proportions
B) variation
C) correlation
D) means

Question 45

Question 46

Use the given process data to construct a control chart for p. A candy manufacturer considers a cracked piece of candy to be a defect. Each day 100 candies are randomly selected and checked for cracks. The numbers of defects for 20
Consecutive days are given below. What is the value of the center line?

A) 10
B) 1.32
C) 6.6
D) 0.066

Question 47

________ variation results from causes that can be identified.

A) Identifiable
B) Assignable
C) Random
D) Definable

Question 48

A control chart for s shown below. Determine whether the process mean is within statistical control. If it is
not, identify which of the three out-of-control criteria lead to rejection of a statistically stable mean.

Question 49

A machine that is supposed to fill small bottles to contain 20 milliliters yields the following data from a test of 4 bottles every hour. What would be the centerline for a control chart for ?

A) 19.935 milliliters
B) 0.380 milliliters
C) 20.000 milliliters
D) 20.212 milliliters

Question 50

Examine the given run chart or control chart and determine whether the process is within statistical control.

A) The process is within statistical control.
B) The process is not within statistical control.

Question 51

A manufacturer of lightbulbs picks 10 lightbulbs at random each day for quality control. The mean and range (in hours) of the lifetimes of the 10 lightbulbs are calculated. The results for 12 consecutive days are shown in
The table below. Construct an R chart to determine whether the process is in statistical control.

A) The process is not within statistical control.
B) The process is within statistical control.

Question 52

Which graph using individual data values instead of a process characteristic?

A) R chart
B) Run chart
C)
D) p chart

Question 53

Use the given process data to construct a control chart for p. A drugstore considers a wait of more than 5 minutes to be a defect. Each week 100 customers are randomly selected and timed at the checkout line. The numbers of defects for
20 consecutive weeks are given below. What is the value of the upper control limit?

A) 0.0622
B) 0.0783
C) 1
D) 6.2

Question 54

A control chart for is shown below. Determine whether the process mean is within statistical control. If it is
not, identify which of the three out-of-control criteria lead to rejection of a statistically stable mean.

Question 55

Examine the given run chart or control chart and determine whether the process is within statistical control.

A) The process is within statistical control.
B) The process is not within statistical control.

Question 56

Examine the given run chart or control chart and determine whether the process is within statistical control.

A) The process is within statistical control.
B) The process is not within statistical control.

Question 57

A ________ is a sequential plot of individual data values over time. One axis is used for the data values, and the other axis is used for the time sequence.

A) flow chart
B) run chart
C) process chart
D) time-process chart

Question 58

A machine is supposed to fill boxes to a weight of 50 pounds. Every 30 minutes a sample of four boxes is tested; the results are given below.
What would be the value of the centerline that would be used in creating an R chart?

A) 11.000 pounds
B) 12.8000 pounds
C) 50 pounds
D) 49.567 pounds

Question 59

Which type of chart would be best for monitoring the proportion of items that are defective?

A) p chart
B) Run chart
C)
D) R chart

Question 60

A run chart for individual values is shown below. Does there appear to be a pattern suggesting that the process
is not within statistical control? If so, describe the pattern.

Question 61

A machine is supposed to fill boxes to a weight of 50 pounds. Every 30 minutes a sample of four boxes is tested;
the results are given below.

Question 62

A machine that is supposed to fill small bottles to contain 20 milliliters yields the following data from a test of 4
bottles every hour.

Question 63

A machine that is supposed to fill small bottles to contain 20 milliliters yields the following data from a test of 4
bottles every hour.

Question 64

A control chart for is shown below. Determine whether the process mean is within statistical control. If it is
not, identify which of the three out-of-control criteria lead to rejection of a statistically stable mean.

Question 65

A machine is supposed to fill boxes to a weight of 50 pounds. Every 30 minutes a sample of four boxes is tested;
the results are given below.

Question 66

A control chart for monitoring variation and center can be based on standard deviations instead of on ranges.
An s chart for monitoring variation is made by plotting sample standard deviations with a centerline at (the
mean of the sample standard deviations) and control limits at , where are found in the
Control Chart Constants table. Construct an s chart for the data below.
A manufacturer of lightbulbs picks 10 lightbulbs at random each day for quality control. The mean, standard
deviation, and range (in hours) of the lifetimes of the 10 lightbulbs are calculated. The results for 12 consecutive
days are shown in the table below.

Question 67

A run chart for individual values is shown below. Does there appear to be a pattern suggesting that the process
is not within statistical control? If so, describe the pattern.

Question 68

A machine is supposed to fill cans that contain 12 ounces. Each hour, a sample of four cans is tested; the results
of 15 consecutive hours are given below.

Question 69

A machine that is supposed to produce ball bearings with a diameter of 7 millimeters yields the following data
from a test of 5 ball bearings every 20 minutes.

Question 70

A machine is supposed to fill boxes to a weight of 50 pounds. Every 30 minutes a sample of four boxes is tested;
the results are given below.

Question 71

A control chart for R is shown below. Determine whether the process variation is within statistical control. If it
is not, identify which of the three out-of-control criteria lead to rejection of statistically stable variation.

Question 72

A machine that is supposed to fill small bottles to contain 20 milliliters yields the following data from a test of 4
bottles every hour.

Question 73

A machine is supposed to fill cans that contain 12 ounces. Each hour, a sample of four cans is tested; the results
of 15 consecutive hours are given below.

Question 74

A machine that is supposed to produce ball bearings with a diameter of 7 millimeters yields the following data
from a test of 5 ball bearings every 20 minutes.

Question 75

A run chart for individual values is shown below. Does there appear to be a pattern suggesting that the process
is not within statistical control? If so, describe the pattern.

Question 76

A machine that is supposed to produce ball bearings with a diameter of 7 millimeters yields the following data
from a test of 5 ball bearings every 20 minutes.

Question 77

A machine is supposed to fill cans that contain 12 ounces. Each hour, a sample of four cans is tested; the results
of 15 consecutive hours are given below.

Question 78

A control chart for R is shown below. Determine whether the process variation is within statistical control. If it
is not, identify which of the three out-of-control criteria lead to rejection of statistically stable variation.

Question 79

A control chart for is shown below. Determine whether the process mean is within statistical control. If it is
not, identify which of the three out-of-control criteria lead to rejection of a statistically stable mean.

Question 80

A manufacturer monitors the level of defects in the television sets that it produces. Each week, 200 television
sets are randomly selected and tested and the number of defects is recorded. The results for 12 consecutive
weeks are shown below.