Deck 16: Statistical Quality Control

Question 1

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

Answer 1

True

Question 2

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

Answer 2

False

Question 3

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

Answer 3

False

Question 4

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

Question 5

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

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

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

Question 8

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

Question 9

Variations that usually occur in a process are called

A) process variations.
B) natural variations.
C) control variations.
D) assignable variations.
E) None of the above

Question 10

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.

Question 11

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

Question 12

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.
E) Even though quality cannot be defined, you know what it is.

Question 13

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.
E) All of the above

Question 14

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

A) assignable variations.
B) control variations.
C) natural variations.
D) process variations.
E) None of the above

Question 15

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

Question 16

Assignable variations in a process are also called natural variations.

Question 17

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) 7.2
E) 10.8

Question 18

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

Question 19

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
E) none

Question 20

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

Question 21

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
E) None of the above

Question 22

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.
E) None of the above

Question 23

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.
E) None of the above

Question 24

R-charts measure changes in

A) central tendency.
B) degree of variation.
C) number of defects per production lot.
D) natural variations.
E) None of the above

Question 25

Table 16-1
Refer to Table 16-1. 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
E) None of the above

Question 26

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
E) None of the above

Question 27

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.
E) None of the above

Question 28

Who introduced control charts in 1924?

A) W. Edwards Deming
B) Philip Crosby
C) J.M. Juran
D) William Shewhart
E) Malcolm Baldrige

Question 29

-charts indicate changes in

A) variation.
B) central tendency.
C) natural variations.
D) numbers of defects.
E) None of the above

Question 30

Table 16-1
Refer to Table 16-1. 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
E) None of the above

Question 31

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
E) None of the above

Question 32

Table 16-1
Refer to Table 16-1. 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.
E) None of the above

Question 33

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
E) None of the above

Question 34

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

A) p-chart
B) x-bar chart
C) R-chart
D) A and B
E) A, B, and C

Question 35

Table 16-1
Refer to Table 16-1. 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
E) None of the above

Question 36

Table 16-1
Refer to Table 16-1. 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.
E) None of the above

Question 37

Table 16-1
Refer to Table 16-1. 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.
E) 37.1258.

Question 38

Table 16-1
Refer to Table 16-1. 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.
E) None of the above

Question 39

Table 16-1
Refer to Table 16-1. 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
E) None of the above

Question 40

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
E) Six Sigma Certification

Question 41

A coffee company is attempting to make certain that all its packaged coffee beans contain the same amount of coffee bean by weight. Over the last few days, it has taken several samples. The overall average weight of the sampled packages is 16 ounces, with an average range of 3 ounces. Each sample was of four packages. What would be the 99.7 upper and lower control limits for an R chart?

Question 42

Table 16-2
Given the sample results (100 units in each sample):
The c-chart is be 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.
E) None of the above

Question 43

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
E) None of the above

Question 44

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
E) None of the above

Question 45

A computer software manufacturer has a toll-free telephone number that customers may use if they have problems or questions about the software. In the past, the company has averaged four calls per hour on a particular product. If a 95.5% c-chart is developed for this, what would the limits be?

Question 46

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

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

Question 47

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
E) 0.0471

Question 48

A computer diskette manufacturer is concerned that some diskettes have bad sectors that would cause a diskette to hold less information than it was intended to hold. In the past, only 5% of these diskettes have had bad sectors. If the company wishes to set 95.5% control limits based on samples of size 500, what would these limits be?

Question 49

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
E) 0.09550

Question 50

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
E) 202.6

Question 51

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
E) 202.6

Question 52

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 53

A p-chart has been developed for a particular item. In the past, 4% of such items have been found to be defective. If a sample of 100 is taken, and 9 of these are found to be defective, should the process be considered out of control based on 95.5% control limits? Explain.

Question 54

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 be the 99.7 percent upper control limit be?

A) 0.1328
B) 0.1085
C) 0.0443
D) 0.1528
E) None of the above

Question 55

A local children's boutique specializes in formal wear for young girls. It has recently hired a new seamstress. To assure the dresses have standard sizes, twenty samples of each 12 dresses that were labeled 3T were sampled. The average length from shoulder to hemline measured 21 inches with a range of 0.5 inches. A sample has just been taken with the following lengths: 21.25, 22.0, 21.5, 20.75, 21.25, 21.35, 21.35, 21.35, 21.35, 21.35, 21.35, and 21.35. Is the new seamstress performing at an acceptable quality level?

Question 56

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
E) None of the above

Question 57

A coffee company is attempting to make certain that all its packaged coffee beans contain the same amount of coffee bean by weight. Over the last few days, it has taken several samples. The overall average weight of the sampled packages is 16 ounces, with an average range of 4 ounces. Each sample was of five packages. What would be the 99.7 upper and lower control limits for an chart?

Question 58

A p-chart has been developed for a particular item. In the past, 4% of such items have been found to be defective. If a sample of 100 is taken, and 9 of these are found to be defective, should the process be considered out of control based on 99.7% control limits? Explain

Question 59

Table 16-2
Given the sample results (100 units in each sample):
Find the 95.5% lower limit of the appropriate p-chart.

A) 0.0076
B) 0.0964
C) 0.2014
D) 0.1397
E) None of the above

Question 60

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 be the 95.5 percent upper control limit be?

A) 0.030
B) 0.000
C) 0.046
D) 0.064
E) None of the above

Question 61

________ are graphs that show upper and lower limits for the process we want to control.

Question 62

A(n) ________ chart is appropriate to monitor the percent defective of a production process.

Question 63

Natural variation of a production process that follows a normal distribution is characterized by two parameters: ________ and ________.

Question 64

A(n) ________ chart is appropriate to monitor the percent of mortalities due to heart problems.

Question 65

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

Question 66

When a process is out of control, ________ variations exist in the process.

Question 67

Match the following.

A) Graphical presentation of process data
B) Range of variables
C) Count of attributes
D) Average of variables
E) Fraction of attributes
p-chart

Question 68

When a process is in control, only ________ variations exist in the process.

Question 69

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

Question 70

A(n) ________ chart is appropriate to monitor the weight of chocolate candy bars.

Question 71

Match the following.

A) Graphical presentation of process data
B) Range of variables
C) Count of attributes
D) Average of variables
E) Fraction of attributes
R-chart

Question 72

The chart one might use to monitor the number of defects per roll of carpet is a ________.

Question 73

If we wish to monitor the number of defects on a page in a printing process, the distribution we base our statistics on is the ________ distribution.

Question 74

A retail store charts the number of customer returns per day. Under normal conditions, the store expects 10 customer returns per day. During the past 10 days, the observed customer returns were as follows: 12, 9, 8, 14, 8, 13, 8, 10, 9, 11. Using 99.7% control limits, is the process under control?

Question 75

Leo Phan is the new business manager at PC Priced Right. He is concerned that his register is incorrectly ringing items. For those items sold during the last seven days, he has counted 10 that were incorrectly charged. What would be the 99.7% control limits for number of incorrect rings per week on this process?

Question 76

A(n) ________ chart is appropriate to monitor the number of needle sticks incurred inadvertently by nurses who are administering medications.

Question 77

If we wish to monitor the average diameter of the hula hoops we are producing, the distribution we base our statistics on is the ________ distribution.

Question 78

________ refers to a quality emphasis that encompasses the entire organization, from supplier to customer.

Question 79

________ introduced control charts in 1924.

Question 80

Match the following.

A) Graphical presentation of process data
B) Range of variables
C) Count of attributes
D) Average of variables
E) Fraction of attributes
chart