Deck 3: Statistical Quality Control

Question 1

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

Answer 1

True

Question 2

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

Answer 2

True

Question 3

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

Answer 3

True

Question 4

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

Question 5

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

Question 6

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

Question 7

Special cause variation can be identified using statistical process control.

Question 8

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

Question 9

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

Question 10

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

Question 11

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

Question 12

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.

Question 13

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

Question 14

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

Question 15

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

Question 16

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

Question 17

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

Question 18

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

Question 19

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

Question 20

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

Question 21

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

Question 22

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

Question 23

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

Question 24

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

Question 25

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

Question 26

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

Question 27

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

Question 28

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

Question 29

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

Question 30

Statistical process control is a subset of statistical quality control.

Question 31

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

Question 32

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

Question 33

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

Question 34

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

Question 35

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

Question 36

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 37

Statistical process control is only effective for service processes.

Question 38

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

Question 39

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

Question 40

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

Question 41

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 42

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

Question 43

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

Question 44

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

Question 45

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

Question 46

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

Question 47

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

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

An R-chart monitors the robustness of a process.

Question 50

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

Question 51

The process centerline for both xbar and R charts are both the same value because they are based on the same raw data.

Question 52

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

Question 53

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

Question 54

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

Question 55

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 56

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 57

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

Question 58

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

Question 59

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

Question 60

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

Question 61

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

Question 62

A company produces a product which is designed to weigh 10 oz. ,with a tolerance of oz.The process produces products with an average weight of 9.95 oz.and a standard deviation of 0.10 oz.According to the process capability ratio is the process capable of meeting design specifications?

A)No,the process capability ratio is less than 1.0
B)Yes,the process capability ratio is less than 1.0
C)No,the process capability ratio is greater than 1.0
D)Yes,the process capability ratio is greater than 1.0

Question 63

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

Question 64

A company produces a product which is designed to weigh 10 oz. ,with a tolerance of oz.The process produces products with an average weight of 9.95 oz.and a standard deviation of 0.10 oz.The process capability ratio for this process is with z = 3.

A)1.67
B)0
C)0.8333
D)-1.67

Question 65

For the process to be capable of meeting design specification the process capability index must be

A)less than one 1.0)
B)equal to or greater than one 1.0)
C)smaller than Six Sigma
D)larger than Six Sigma

Question 66

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

Question 67

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

Question 68

A company produces a product which is designed to weigh 10 oz. ,with a tolerance of oz.The process produces products with an average weight of 9.95 oz.and a standard deviation of 0.10 oz.The process capability index for this process with z = 3 is

A)1.50
B)-1.50
C)1.83
D)-1.83

Question 69

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

Question 70

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

Question 71

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

Question 72

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

Question 73

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

Question 74

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

Question 75

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

Question 76

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

Question 77

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

Question 78

A control chart that reflects the amount of dispersion,or spread,present within each sample is known as an)

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

Question 79

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 80

A process is generally considered to be in control when

A)there are no sample points outside the control limits
B)most points are near the center line,without many being close to the control limits
C)sample points are randomly distributed equally above and below the center line
D)all of the above are true