Deck 25: Process Capability and Spc

Question 1

Attributes are those quality characteristics that are classified as either conforming or not conforming to specifications.

Answer 1

True

Question 2

The "p" chart is only useful for sampling that deals with continuous variables.

Answer 2

False

Question 3

An example of assignable variation in a production system may be that a machine is not adjusted properly.

Answer 3

True

Question 4

To obtain a 99.7 percent confidence level in a "p" chart we would use a value of 3 for "z".

Question 5

In acceptance sampling,the number of units in the sample (n)is determined by the interaction of the acceptable quality level (AQL),the lot tolerance percent defective (LTPD),the probability of rejecting a high quality lot (alpha)and the probability of accepting a low quality lot (beta).

Question 6

If the fraction defective is 0.12 based on a sample size of 16,the standard deviation used in the "p" chart is about 0.08.

Question 7

Variation that is inherent in a production process itself is called assignable variation.

Question 8

Process control is concerned with monitoring quality after the product or service has been produced.

Question 9

An example of assignable variation in a production system may be that workers are not identically trained.

Question 10

Statistical process control involves testing random samples of output from a process to determine whether the process is producing items within a pre-selected range.

Question 11

If the fraction defective is 0.4 based on a sample size of 100,the standard deviation used in the "p" chart is about 0.10.

Question 12

Variation in production systems that is caused by factors that can be clearly identified and possibly even managed is called assignable variation.

Question 13

Measurement by attributes means taking a sample,measuring the attribute in question and determining the level of quality in the population from which the sample was drawn.

Question 14

It is impossible to have zero variability in production processes.

Question 15

The value for "z" used in quality control charts is based on the degree of confidence you want to have in the resulting UCL and LCL values.

Question 16

Variation that is inherent in a production process itself is called common variation.

Question 17

The capability index is used to gauge economic changes in service systems.

Question 18

Acceptance sampling is performed on goods that already exist to determine what percentage of items conforms to specifications.

Question 19

A quality control chart has upper and lower control limits expressed as lines on a chart.As long as the sample values fall between these two lines there is no need to investigate process behavior.

Question 20

Genichi Taguchi's view of the cost of quality is that variance is a discontinuous function.

Question 21

In monitoring process quality we might use which of the following statistics?

A)Absolute values
B)Percentage deviation from tolerance centers
C)"k" values for the sample mean
D)Logarithmic control intervals
E)Difference between the highest and lowest value in a sample

Question 22

You have just used the capability index (C_pk)formulas to compute the two values "min [1.5,1]".Which of the following is the interpretation of these numbers?

A)The true capability index value is 1
B)The mean of the production process has shifted to the left of the design limits
C)The mean of the production process has shifted to the right of the design limits
D)The mean has not shifted at all
E)The true capability index value is between 1.5 and 1

Question 23

In acceptance sampling,the value for the acceptance number (c)is determined by the interaction of the acceptable quality level (AQL),the lot tolerance percent defective (LTPD),the probability of rejecting a high quality lot (alpha)and the probability of accepting a low quality lot (beta).

Question 24

The producer's risk associated with rejecting a high quality lot is denoted in acceptance sampling with the Greek letter beta.

Question 25

You have just used the capability index (C_pk)formulas to compute the two values "min [2,2.5]".Which of the following is the proper interpretation of these numbers?

A)The true capability index value is 2.5
B)The mean of the production process has shifted to the left of the design limits
C)The mean of the production process has shifted to the right of the design limits
D)The mean has not shifted at all
E)The true capability index value is between 2 and 2.5

Question 26

Quality control charts usually have a central line and upper and lower control limit lines.Which of the following are reasons that the process being monitored with the chart should be investigated?

A)A single plot falls above or below the control limits
B)Normal behavior
C)A large number of plots are on or near the central line
D)No real trend in any direction
E)A change in raw materials or operators

Question 27

The probability associated with rejecting a high quality lot is denoted in acceptance sampling with the Greek letter alpha.

Question 28

The Greek letter alpha is associated with consumer's risk.

Question 29

Standard practice in statistical process control for variables is to set control limits so that 95 percent of the sample means will fall within the UCL and the LCL.

Question 30

Quality control charts usually have a central line and upper and lower control limit lines.Which of the following is not a reason that the process being monitored with the chart should be investigated?

A)A large number of plots are close to the upper or lower control lines
B)Erratic behavior of the plots
C)A single plot falls above or below the control limits
D)A change in raw materials or operators
E)A run of five above the central line

Question 31

You have just used the capability index (C_pk)formulas to compute the two values "min [1,1]".Which of the following is the proper interpretation of these numbers?

A)The true capability index value is exactly 1
B)The mean of the production process has shifted to the left of the design limits
C)The mean of the production process has shifted to the right of the design limits
D)The mean has not shifted at all
E)None of the above

Question 32

The probability associated with accepting a low quality lot is denoted in acceptance sampling with the Greek letter alpha.

Question 33

In variables sampling the actual measurements of the variable observed are used regardless of whether the unit is good or bad.

Question 34

One-hundred percent inspection is justified when the cost of inspection is low.

Question 35

AQL stands for accepting questionable lots in production quality management.

Question 36

Sampling plans are generally displayed graphically through the use of operating characteristic (OC)curves.

Question 37

The capability index (C_pk)indicates the position of the mean and tails of a processes variance relative to design specifications

Question 38

LTPD in acceptance sampling stands for "lots of tolerance for parts defective".

Question 39

The capability index (C_pk)calculates the percentage of items being produced within specifications.

Question 40

Total,one-hundred percent,inspection can never be cost justified.

Question 41

You want to determine the upper control line for a "p" chart for quality control purposes.You take several samples of a size of 100 items in your production process.From the samples you determine the fraction defective is 0.05 and the standard deviation is 0.01.If the desired confidence level is 99.7 percent,which of the following is the resulting UCL value for the line?

A)0.39
B)0.08
C)0.06
D)0.05
E)None of the above

Question 42

You are developing an "X-bar" chart based on sample means.You know the standard deviation of the sample means is 4,the desired confidence level is 99.7 percent and the average of the sample means is 24.Which of the following is your UCL?

A)36
B)24
C)12
D)4
E)None of the above

Question 43

You want to determine the control lines for a "p" chart for quality control purposes.If the total number of defects from all samples is 560,the number of samples is 70 and the sample size is 80,which of the following would be the standard deviation used in developing the control lines?

A)0.9000
B)0.4556
C)0.0335
D)0.0011
E)0.0112

Question 44

You want to develop a three-sigma "R" chart.You know the average range is 12 based on several samples of size 6.Which of the following is the resulting LCL?

A)20.0
B)18.3
C)7.02
D)5.6
E)0.0

Question 45

If there are 400 total defects from 8 samples,each sample consisting of 20 individual items in a production process,which of the following is the fraction defective that can be used in a "p" chart for quality control purposes?

A)400
B)160
C)2.5
D)1.0
E)0.4

Question 46

For which of the following should we use a "p" chart to monitor process quality?

A)Defective electrical switches
B)Errors in the length of a pencil
C)Weight errors in cans of soup
D)Temperature of entrees in a restaurant
E)Letter grades on a final examination

Question 47

With which of the following should we use an "X-bar" chart based on sample means to monitor process quality?

A)Grades in a freshman "pass/fail" course
B)Tire pressures in an auto assembly plant
C)Vehicles passing emissions inspection
D)Computer software errors
E)Number of units with missing operations

Question 48

You want to determine the control lines for a "p" chart for quality control purposes.If the desired confidence level is 99 percent,which of the following values for "z" would you use in computing the UCL and LCL?

A)0.99
B)2
C)2.58
D)3
E)None of the above

Question 49

Which of the following should we use an "R" chart to monitor process quality?

A)Weighing trucks at a highway inspection station to determine if they are overloaded
B)Deciding whether an airliner has sufficient fuel for its trip
C)Student grades measured from 1 to 100
D)Determining whether vehicles from a motor pool will run
E)Determining the accuracy of a forecast of "snow"

Question 50

Processes produce goods and services that have some measurable variation in attributes.What is the quality philosophy that companies which insist on design tolerances set six standard deviations of attribute variation away from the mean are operating under?

Question 51

You are developing an "X-bar" chart based on sample means.You know the standard deviation of the sample means is 4,the desired confidence level is 99 percent and the average of the sample means is 20.Which of the following is your LCL?

A)36
B)24
C)9.68
D)16.79
E)30.32

Question 52

For which of the following should we use a "p" chart to monitor process quality?

A)The dimensions of brick entering a kiln
B)Lengths of boards cut in a mill
C)The weight of fluid in a container
D)Grades in a freshman "pass/fail" course
E)Temperatures in a classroom

Question 53

If there are 120 total defects from 10 samples,each sample consisting of 10 individual items in a production process,which of the following is the fraction defective that can be used in a "p" chart for quality control purposes?

A)120
B)10
C)8
D)1.2
E)0.8

Question 54

You want to determine the lower control line for a "p" chart for quality control purposes.You take several samples of a size of 50 items in your production process.From the samples you determine the fraction defective is 0.006 and the standard deviation is 0.001.If the desired confidence level is 99.7 percent,which of the following is the resulting LCL value for the line?

A)0.0
B)0.002
C)0.003
D)0.004
E)None of the above

Question 55

If you are going to develop an "R" chart based on range statistics and you are using a sample size of 9 for your charting purposes.Which of the following is the lower control limit D3 factor for the chart?

A)0.08
B)0.14
C)0.18
D)0.22
E)0.29

Question 56

If you are going to develop an "R" chart based on range statistics and you are using a sample size of 15 for your charting purposes.Which of the following is the upper control limit D4 factor for the chart?

A)1.65
B)1.70
C)1.76
D)1.87
E)1.92

Question 57

You want to develop a three-sigma "R" chart.You know the average range is 5 based on several samples of size 10.Which of the following is the resulting UCL?

A)20.9
B)8.9
C)7.02
D)5
E)3.1

Question 58

Which of the following should we use an "R" chart to monitor process quality?

A)Grades in a freshman "pass/fail" course
B)Tire pressures in an auto assembly plant
C)Vehicles passing emissions inspection
D)Computer software errors
E)Number of units with missing operations

Question 59

You want to determine the control lines for a "p" chart for quality control purposes.If the total number of defects from all samples is 2,500,the number of samples is 100 and the sample size is 50,which of the following would be the standard deviation used in developing the control lines?

A)0.4900
B)0.2499
C)0.1556
D)0.0707
E)0.02499

Question 60

If you are going to develop an "X-bar" chart based on range statistics and you are using a sample size of 12 for your charting purposes.Which of the following is the A2 factor for the "X-bar" chart?

A)0.37
B)0.31
C)0.27
D)0.22
E)0.18

Question 61

Explain the difference between producer's risk and consumer's risk in acceptance sampling.

Question 62

What is the difference between statistical process control (SPC)and statistical quality control (SQC)?

Question 63

What does it mean when we say that a process is capable?

Question 64

You want to determine the control lines for a "p" chart for quality control purposes.If the total number of defects from all samples is 560,the number of samples is 70 and the sample size is 80,what would be the standard deviation used in developing the control lines?

Question 65

You want to develop a three-sigma "R" chart.You know the average range is 12 based on several samples of size 6.Which of the following is the resulting LCL?

Question 66

You are developing an "X-bar" chart based on sample means.You know the standard deviation of the sample means is 4,the desired confidence level is 99.7 percent and the average of the sample means is 24.What is your UCL?

Question 67

You are developing an "X-bar" chart based on sample means.You know the standard deviation of the sample means is 4,the desired confidence level is 99 percent and the average of the sample means is 20.What is your LCL?

Question 68

If the fraction defective is 0.12 based on a sample size of 16,what is the standard deviation to be used when constructing a "p" chart?

Question 69

If the fraction defective is 0.4 based on a sample size of 100,what is the standard deviation used in constructing the "p" chart?

Question 70

All else being equal,how large is the effect of lot size on sample size?

Question 71

You want to determine the control lines for a "p" chart for quality control purposes.If the total number of defects from all samples is 2,000,the number of samples is 100 and the sample size is 50,what would be the standard deviation used in developing the control lines?

Question 72

You want to develop a three-sigma "R" chart.You know the average range is 5 based on several samples of size 10.Which of the following is the resulting UCL?

Question 73

What is the symbol designating the capability index?

Question 74

You have 75 total defects from 100 different samples of 15.What is p?

Question 75

Lots are defined as low quality when the percentage of defective units is greater than what?