Deck 15: Statistical Quality Control

Question 1

TQM emphasizes quality of the goods or service-producing division of the company.

Answer 1

False

Question 2

A p-chart could be used to monitor the average weight of cereal boxes.

Answer 2

False

Question 3

If we are tracking quality of performance for a class of students, we should plot the individual grades on an x-bar chart, and the pass/fail result on a p-chart.

Answer 3

True

Question 4

P-charts and c-charts are examples of control charts for variables.

Question 5

An x-bar chart would be appropriate to monitor the number of defects in a production lot.

Question 6

A c-chart would be appropriate to monitor the number of weld defects on the steel plates of a ship's hull.

Question 7

It is impossible to develop a process that has zero variability.

Question 8

Technically, to achieve Six Sigma quality, there would have to be fewer than 3.4 defects per million opportunities.

Question 9

Samples sizes of five are often used when building control charts.

Question 10

If we are attempting to control the diameter of bowling balls, we will find a p-chart to be quite helpful.

Question 11

C-charts are used to analyze the proportion defective in a sample.

Question 12

The central limit theorem provides the statistical foundation for control charts.

Question 13

Assignable variations in a process are also called natural variations.

Question 14

Statistical process control uses regression and other forecasting tools to help control processes.

Question 15

If all of the control points on a control chart lie between the UCL and the LCL, the process is always in control.

Question 16

The independent axis of a control chart is time.

Question 17

W.Edwards Deming introduced control charts in the 1920s.

Question 18

Robert Pirsig defines quality as "Fitness for use."

Question 19

The underlying distribution for a p-chart is binomial.

Question 20

The U.S.government awards for quality achievement are called the Malcolm Baldrige National Quality Awards.

Question 21

charts indicate changes in

A)variation.
B)central tendency.
C)natural variations.
D)numbers of defects.

Question 22

A company believes a process monitored by an x-bar chart to be in control.When the most recent control point exceeded the UCL value by 20%, the company should

A)believe that a random bad luck chance occurred and proceed.
B)suspect that an assignable cause of variation now exists and can be found.
C)ignore the control point completely, as it is simply an outlier.
D)wait for the next four samples to be taken to see if a trend develops.

Question 23

Table 15-1

Refer to Table 15-1.Bags of chocolate candy are sampled to ensure proper weight.The overall average for the samples is 36 ounces.Each sample contains eight bags.The average range is 1.3 ounces.The lower control chart limit for the sample averages would be

A)36.3730.
B)36.4849.
C)35.6270.
D)35.5150.

Question 24

Table 15-1

Refer to Table 15-1.Bags of chocolate candy are sampled to ensure proper weight.The overall average for the samples is 36 ounces.Each sample contains twelve bags.The average range is 1.3 ounces.The upper control chart limit for the sample averages would be

A)36.3458.
B)35.6542.
C)38.3101.
D)36.6279.

Question 25

For data that are appropriately handled by C-charts, the mean equals the variance.

Question 26

Which of the following is not a popular definition of quality?

A)Quality is the totality of features and characteristics of a product or service that bears on its ability to satisfy stated or implied needs.
B)Quality is defined as a competitively priced product that surpasses customer needs.
C)Quality is the degree to which a product conforms to design or specification.
D)Quality is fitness for use.

Question 27

All that is required to develop limits for a C-chart is knowledge of the average count of defects.

Question 28

The area from two standard deviations above to two standard deviations below the mean of a normal distribution will contain 99.7% of all of the area under the curve.

Question 29

Bags of pretzels are sampled to ensure proper weight.The overall average for the samples is 9 ounces.Each sample contains 25 bags.The standard deviation is estimated to be 3 ounces.The upper control chart limit (for 99.7% confidence)for the average would be ________ ounces.

A)9.4
B)18.0
C)10.2
D)10.8

Question 30

Variations that usually occur in a process are called

A)process variations.
B)natural variations.
C)control variations.
D)assignable variations.

Question 31

Control charts that are used to monitor processes that are measured in continuous units are classified as which of the following?

A)control charts for attributes
B)control charts for variables
C)control charts for defects
D)control charts for quality

Question 32

R-charts measure changes in

A)central tendency.
B)degree of variation.
C)number of defects per production lot.
D)natural variations.

Question 33

The -chart would be useful when we

A)took a number of measurements and computed the average.
B)took a number of measurements and computed the ranges.
C)found the fraction of the production lot defective.
D)found the number of defective items in a production lot.

Question 34

Variations that need not occur in production processes are referred to as

A)assignable variations.
B)control variations.
C)natural variations.
D)process variations.

Question 35

The inspection of cans of juice involves sampling some cans and weighing them.The overall average for the samples is 39 ounces.Each sample contains 36 cans.The standard deviation is estimated to be 2 ounces.The 99.7% lower control chart limit for the average would be

A)37.67.
B)38.00.
C)39.33.
D)40.00.

Question 36

The R-chart would be useful when we

A)took a number of measurements and computed the average.
B)took a number of measurements and computed the ranges.
C)found the fraction of the production lot defective.
D)found the number of defective items in a production lot.

Question 37

Table 15-1

Refer to Table 15-1.To guarantee that cans of soup are properly filled, some cans are sampled and the amounts measured.The overall average for the samples is 12 ounces.Each sample contains 10 cans.The average range is 0.4 ounces.The upper control chart limit for the sample averages would be

A)12.1232.
B)11.8768.
C)13.2.
D)12.308.

Question 38

Who introduced control charts in 1924?

A)W.Edwards Deming
B)Philip Crosby
C)J.M.Juran
D)Walter Shewhart

Question 39

The central limit theorem states that the distribution of x-bars will tend to follow a normal distribution as long as the population they are drawn from is normally distributed.

Question 40

A run of four consecutive points above the center line is a sufficient reason to stop the process and investigate for cause.

Question 41

Which of the following control charts is/are for variables?

A)x-bar chart only
B)R-chart only
C)p-chart only
D)both x-bar and R-charts

Question 42

Defects in computer hard-drives will usually render the entire computer worthless.For a particular model, the percent defective in the past has been 1%.If a sample size of 400 is taken, what would the 95.5% lower control chart limit be?

A)0.00995
B)0.00005
C)0.00000
D)0.01000

Question 43

The p-chart would be useful when we

A)took a number of measurements and computed the average.
B)took a number of measurements and computed the ranges.
C)found the fraction of the production lot defective.
D)found the number of defective items in a production lot.

Question 44

Which of the following statements is false regarding control charts?

A)X-bar charts measure central tendency in a process.
B)R-charts measure the variability of a process.
C)It is not possible to have a LCL below 0 in a c-chart.
D)The nominal line is always the midpoint between the UCL and LCL.

Question 45

A quality control program is being developed for batteries.The percent defective for these in the past has been 3%.If a sample size of 120 is taken, what would the 99.7% upper control chart limit be?

A)0.0812
B)0.0767
C)0.0611
D)0.0307

Question 46

A p-chart is based on which of the following probability distributions?

A)Poisson
B)binomial
C)uniform
D)exponential

Question 47

Which of the following control charts is/are for attributes?

A)x-bar chart only
B)R-chart only
C)p-chart only
D)both x-bar and R-charts

Question 48

Table 15-1

Refer to Table 15-1.To guarantee that cans of soda are properly filled, some cans are sampled and the amounts measured.The overall average for the samples is 12 ounces.Each sample contains 10 cans.The average range is 0.4 ounces.The lower control chart limit for the sample averages would be

A)12.1232.
B)11.8768.
C)13.2.
D)12.308.

Question 49

Table 15-1

Refer to Table 15-1.The Pristine Paint Company produces paint in gallon cans.They have found that in more than 10 samples of 8 cans each, the average gallon can contains 1.1 gallons of paint.The average range found over these samples is 0.15 gallons.What is the upper control limit for the sample averages in this process?

A)1.100
B)1.150
C)1.268
D)1.156

Question 50

A c-chart is based on which of the following probability distributions?

A)Poisson
B)binomial
C)uniform
D)exponential

Question 51

The U.S.government award for quality achievement is the

A)Deming Prize.
B)Shewhart Symbol of Excellence.
C)Malcolm Baldrige National Quality Award.
D)Bush Award for Quality Management.

Question 52

Table 15-1

Refer to Table 15-1.The average range of a process for packaging cereal is 1.1 ounces.If the sample size is 10, find the lower control chart limit for the range chart.

A)0.245
B)1.955
C)1.777
D)0.223

Question 53

Table 15-1

Refer to Table 15-1.Bags of tea are sampled to ensure proper weight.The overall average for the samples is 8 ounces.Each sample contains 10 bags.The average range is 0.1 ounces.What is the lower limit of the sample averages chart?

A)7.9692
B)8.0308
C)7.9076
D)8.0924

Question 54

An airline company tracks the number of lost bags that occur each day.This is best monitored by which of the following control charts?

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

Question 55

Defects in marble countertops usually require the whole top to be reconstructed.In one kitchen shop, the percent defective in the past has been one percent.If a sample size of 30 is taken, what should the 95.5 percent upper control limit be?

A)0.030
B)0.000
C)0.046
D)0.064

Question 56

A coffee dispenser is supposed to dispense coffee into an 8 o.z.cup.The average amount of coffee filled into the cup must be below 7.9.This is best monitored by which of the following control charts?

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

Question 57

When receiving a shipment from a supplier, inspection must be done to check the fraction of defective products.This is best monitored by which of the following control charts?

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

Question 58

Defects in the finish of new, custom automobiles usually require the whole body to be repainted.In one "custom" shop, the percentage of defective finishes has been 2 percent.If a sample size of 10 is taken, what should the 99.7 percent upper control limit be?

A)0.1328
B)0.1085
C)0.0443
D)0.1528

Question 59

Table 15-1

Refer to Table 15-1.The average range of a process for packaging cereal is 1.1 ounces.If the sample size is 10, find the upper control chart limit for the range chart.

A)0.245
B)1.955
C)1.777
D)0.223

Question 60

A plant manager is concerned with the variability of beer being filled in 12 oz.cans.The most appropriate control chart would be which of the following?

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

Question 61

The standard deviation of a process can be described as

A)a measure of dispersion.
B)the average value.
C)a measure of central tendency.
D)assignable variations.

Question 62

Joe studied his control chart and noticed it had been built with repeated samples of ten units and three sigma limits that were UCL = 109.0125 and LCL = 90.9875.What is the process standard deviation?

A)9.5
B)6.7
C)5.2
D)3

Question 63

Table 15-2
Given the sample results (100 units in each sample):

Based on Table 15-2, find the 95.5% lower limit of the appropriate p-chart.

A)0.0076
B)0.0964
C)0.2014
D)0.1397

Question 64

A company has been receiving complaints about the attitude of some sales clerks.Over a 10-day period, the total number of complaints was 360.The company wishes to develop a control chart for the number of complaints.What would the upper control limit on the number of complaints per day be for a 2 sigma (95.5%)control chart?

A)12
B)42
C)48
D)54

Question 65

Which of these patterns on a control chart would require a worker to stop the process and investigate for an assignable cause?

A)a run of three consecutive points above the center line
B)a trend run of six consecutive points all decreasing
C)six consecutive points close to the center line
D)one point near the lower control limit

Question 66

The c-chart is useful when we

A)take a number of measurements and compute the average.
B)take a number of measurements and compute the ranges.
C)find the fraction of the production lot defective.
D)find the number of defective items in a production lot.

Question 67

A company has been receiving complaints about the attitude of some sales clerks.Over a 10-day period, the total number of complaints was 250.The company wishes to develop a control chart for the number of complaints.What would the upper control limit on the number of complaints per day be for a 2 sigma (95.5%)control chart?

A)35
B)40
C)50
D)200

Question 68

Table 15-1

Use the data shown below and the information in Table 15-1 to develop an upper control limit for a control chart that monitors consistency.What is the upper control limit?

A)2.11
B)6.38
C)10.82
D)1.17

Question 69

A company has been receiving complaints about the attitude of some sales clerks.Over a 10-day period, the total number of complaints was 250.The company wishes to develop a control chart for the number of complaints.What would the lower control limit on the number of complaints per day be for a 3 sigma (99.7%)control chart?

A)20
B)0
C)15
D)10

Question 70

The mean of a process can be described as

A)a measure of dispersion.
B)the average value.
C)the standard deviation.
D)a measure of consistency.

Question 71

Baker studied his control chart and noticed it had been built with repeated samples of eight units and three sigma limits that were UCL = 73.07 and LCL = 58.93.What is the process standard deviation?

A)2.35
B)6.67
C)5.26
D)3.33

Question 72

Which of these patterns on a control chart would require a worker to stop the process and investigate for an assignable cause?

A)a run of five points alternating up and down
B)a run of three consecutive points above the center line
C)two out of three points close to the center line
D)one point below the lower control limit

Question 73

A company has been receiving complaints about the attitude of some sales clerks.Over a 10-day period, the total number of complaints was 250.The company wishes to develop a control chart for the number of complaints.What would the lower control limit on the number of complaints per day be for a 2 sigma (95.5%)control chart?

A)20
B)0
C)15
D)10

Question 74

Which of these patterns on a control chart would require a worker to stop the process and investigate for an assignable cause?

A)a run of five consecutive points below the center line
B)a run of three consecutive points all increasing
C)six consecutive points close to the center line
D)one point near the lower control limit

Question 75

Technically, to achieve Six Sigma quality, there would have to be fewer than ________ defects per million opportunities.

A)6
B)166,667
C)67
D)3.4

Question 76

A 400-student lecture in introductory statistics conducted by a tenured professor breaks into 20 sections of 20 students for problem sessions run by helpful graduate assistants that give weekly quizzes to lighten the mood.The graduate assistants determine their section averages for their quiz each week and compare the numbers.Which of these statements is best?

A)The standard deviation of the section averages should approach the overall standard deviation.
B)A graduate assistant whose section quiz average falls outside three sigma limits should be replaced.
C)For any given week, the section averages should be normally distributed.
D)95.5% of the section averages should fall within three standard deviations of the overall average.

Question 77

A company is producing cylindrical blocks for a children's toy.The average diameter of a block is 3.5 inches.Sixteen blocks are inspected and the diameters are measured.The standard deviation is estimated to be 0.02 inches.What are the 99.7% upper and lower control limits for the x-bar chart?

Question 78

Samaje studied his control chart and noticed it had been built with repeated samples of five units and three sigma limits that were UCL = 51.71 and LCL = 38.29.What is the process standard deviation?

A)3
B)1.732
C)2.236
D)5

Question 79

A company has been receiving complaints about the attitude of some sales clerks.Over a 10-day period, the total number of complaints was 360.The company wishes to develop a control chart for the number of complaints.What would the upper control limit on the number of complaints per day be for a 3 sigma (99.7%)control chart?

A)18
B)36
C)42
D)54

Question 80

Table 15-1

Use the data shown below and the information in Table 15-1 to develop an upper control limit for a control chart that monitors central tendency.What is the upper control limit?

A)0
B)1.17
C)10.82
D)11.99