Deck 3: Statistical Process Control

Question 1

Unique or special cause variation reflects the random variation associated with the output of a process.

Answer 1

False

Question 2

Process control is achieved by taking periodic samples from a process and plotting the sample points on a chart to determine if the process is within control limits.

Answer 2

True

Question 3

Employee training in statistical process control is a fundamental principle in total quality management programs.

Answer 3

True

Question 4

Process control charts are often used at a critical point after which it is difficult to correct or rework the process output.

Question 5

One reason some companies fail in their attempt to apply statistical process control is lack of training.

Question 6

Statistical process control involves monitoring and controlling a process to prevent poor quality.

Question 7

Process control charts are rarely useful for monitoring and controlling the output of service processes.

Question 8

Control limits are based on the special cause variation inherent in a process.

Question 9

Statistical process control is a tool used to monitor and improve quality.

Question 10

Special cause variation can be identified using statistical process control.

Question 11

Statistical process control is based on a philosophy of inspection as opposed to prevention.

Question 12

Control charts visually show when a process is not within statistical control limits.

Question 13

After special cause variation is detected,the focus changes to identifying the root cause of the variation and eliminating it.

Question 14

A process that is determined to be in control contains no variation.

Question 15

Common cause (random)variation provides evidence that the process is not in control.

Question 16

Statistical process control is only effective for service processes.

Question 17

One goal of statistical process control is to prevent a process from producing items that have to be scrapped or reworked.

Question 18

Statistical process control is a subset of statistical quality control.

Question 19

Two types of variation associated with the output of a process are common (random)cause and special cause.

Question 20

All processes contain a certain amount of variation in their output.

Question 21

A quantitative variable classifies while a qualitative variable (attribute)measures.

Question 22

Attribute (qualitative)control charts are used to monitor descriptive characteristics of the output of a process.

Question 23

The formula used to determine the upper and lower control limits is based on specification limits.

Question 24

When constructing a control chart for the first time,all points should be within the control limits indicating the process is in control.

Question 25

A p-chart is used to monitor the proportion defective in the output of a process.

Question 26

Defect and defective mean the same thing for attribute (qualitative)control charts.

Question 27

Control charts are never implemented until special cause variation has been detected in a process.

Question 28

The range measures the variation within samples versus the variation between samples.

Question 29

A c-chart monitors the number of defects in small samples.

Question 30

Construction and use of an -chart is based on an assumption that the sample points are normally distributed around the centre line.

Question 31

It is sometimes not necessary to determine new control limits after special cause variation has been identified if the source has been eliminated without changing the process.

Question 32

When calculating control limits for a process,the number of standard deviations (z value)is typically six.

Question 33

When monitoring a process's output with a quantitative variable either an R-chart or an -chart is used,but never both.

Question 34

The smaller the historical proportion defective reported for a process,the larger the sample size required to detect special cause variation with a p-chart.

Question 35

With a c-chart,the sample size is small and often contains only one item.

Question 36

The individual that detects special cause variation in a process is not allowed to diagnose the root cause and correct it.

Question 37

When special cause variation is detected,it is normally eliminated by increasing the number of standard deviations (z value)used to calculate the control limits.

Question 38

The range is the difference between the smallest and largest values in a sample.

Question 39

When a control chart detects no special cause variation in a process,the upper and lower control limits are the same value.

Question 40

Variable control charts are used for quantitative measures such as weight or time.

Question 41

Statistical process control can prevent poor quality before it occurs if a pattern is evident in the plotted points.

Question 42

In some cases,the -chart is used without the R-chart because the within sample variation is not of concern.

Question 43

Only certified statisticians should use Excel to construct a control chart for a process.

Question 44

Control chart sample sizes are becoming smaller because it is easier to detect a pattern with Excel or other data analysis software.

Question 45

In some cases,the -chart is used without an R-chart because there is no variation between the samples.

Question 46

A sequence of sample points that display a pattern is known as a run.

Question 47

It is possible to have low variation within samples while at the same time having high variation between sample means.

Question 48

If a pattern is evident in the points plotted on a control chart,the points are always considered evidence that the process is in control.

Question 49

The popularity of Excel and other data analysis software has been a major factor in the increased use of statistical process control.

Question 50

A pattern test can identify an out-of-control process even if all sample points are within control limits.

Question 51

A control chart is in control when the plot of the sample points exhibits a pattern.

Question 52

One advantage of using a pattern test is that special cause variations may be identified before any points are plotted outside the control limits.

Question 53

Information from an R-chart can be used to construct the control limits for an -chart.

Question 54

If the points plotted on a control chart display a pattern,it is called a run.

Question 55

Using Excel to construct control charts should be avoided because most people believe using software results in too many errors.

Question 56

The R-chart is used for monitoring and controlling variation within samples.

Question 57

Variable (quantitative)control charts are used to monitor measurable characteristics of a process's outputs.

Question 58

The process centre line for both and R-charts are both the same value because they are based on the same raw data.

Question 59

An R-chart monitors the robustness of a process.

Question 60

An and R-chart constructed to monitor and control a process use same raw data.

Question 61

Excel can be used to increase the efficiency and accuracy of determining the process capability ratio and the process capability index.

Question 62

Possible root causes of special cause variation include all of the following except

A)operator error.
B)process out of adjustments.
C)over producing.
D)defective materials.

Question 63

A process capability ratio greater than one shows that a process is capable of producing output within its specification limits.

Question 64

Which of the following is not a characteristic of a control chart?

A)The centre line is determined using special cause variations.
B)The upper and lower control limits are based on special cause variation.
C)The centre line is determined by using the target value.
D)None of the above are true.

Question 65

The process capability ratio measures the specification limits over the control limits.

Question 66

The process capability index indicates how much a process mean differs from the target specification value.

Question 67

The goal of statistical process control is to ensure that the control limits and specifications limits for a process always remain the same.

Question 68

For a given process,the process capability ratio is not related to its control limits.

Question 69

Four common types of control charts include all of the following except

A) -chart
B)t-chart
C)p-chart
D)c-chart

Question 70

A process capability ratio reflects the number of (Z)sigmas included in the range between the upper and lower control limits.

Question 71

Design specification limits should always be wider than the control limits for a given process.

Question 72

Which of the following statements concerning control chart limits is true?

A)The smaller the value of z,the more narrow the control limits are and the more sensitive the chart is to changes in the production process.
B)The larger the value of z,the more narrow the control limits are and the more sensitive the chart is to changes in the production process.
C)The smaller the value of z,the wider the control limits are and the less sensitive the chart is to changes in the production process.
D)The larger the value of z,the more narrow the control limits are and the less sensitive the chart is to changes in the production process.

Question 73

Tolerances and specification limits report similar information for a given product design.

Question 74

Special cause variation in a process is more likely to be detected with

A)wider control limits.
B)narrow control limits.
C)wider specification limits.
D)narrow specification limits.

Question 75

Which of the following is not a primary purpose of statistical process control?

A)to establish control limits
B)to detect special cause variations
C)to identify specification limits
D)to determine when a process is not in control

Question 76

Tolerances reflect the amount of common cause variation allowed in a process.

Question 77

The process capability index is used only for p and c charts while the process capability ratio is used only for and R charts.

Question 78

Which of the following statements is true?

A)With wider control limits (larger Z),the process is more likely to be in control.
B)With narrower control limits,(smaller Z),the process is more likely to be in control.
C)With wider control limits (larger Z),the process is less likely to be in control.
D)None of the above are true.

Question 79

Some companies that strive to provide extremely high quality use Z=6 (six sigma)vs.Z=3 (three sigma)when constructing control limits.

Question 80

A control chart that uses the actual number of defects per item to monitor a process is known as a

A)p-chart.
B)c-chart.
C)R-chart.
D) -chart.