Deck 22: Quality Control

Question 1

An importer of decorative ceramic tile samples 50 tiles each day from incoming shipments.Some tiles are cracked or broken before or during transit, rendering them useless scrap.Sampling from incoming shipments for 30 days reveals that a total of 250 tiles are cracked or broken.The lower and upper control limits on the p chart for these data are ________________________ .

A)0.067 and 0.299
B)0.157 and 0.177
C)0 and 0.299
D)1.314 and 10.886
E)0.009 and 0.325

Answer 1

0.009 and 0.325

Question 2

A producer of specialty products uses a variety of natural and man-made materials to make unique countertops for kitchens and baths.One product line mixes concrete and natural river stone to make countertops that are polished to a high shine revealing unique patterns.Occasionally coarse sand will result in undesirable pitting and rough spots on surfaces.Consequently, as part of its quality control efforts, 8 by 4 foot polished slabs are checked periodically for imperfections.For each slab inspected the number of imperfections (pits, rough spots, etc.) is recorded.What type of control chart should be used for these data?

A)Individuals chart
B)P-chart
C)C-chart
D)X-bar and R charts
E)ARL chart

Answer 2

C-chart

Question 3

An automatic filling process is used to dispense hand sanitizer into small purse size bottles.The target weight is 75 ml.The company has initiated control charting to stabilize and improve the automatic filling process.For each of twenty-five samples consisting of four bottles, the contents were measured and the mean weight and range were determined.The average of the means across all samples was found to be 72.5 ml.and the average range was 2.75 ml.The control limits for the X-bar chart are ________________________ .

A)68.48 and 76.52 ml
B)71.16 and 73.84 ml
C)70.49 and 74.51 ml
D)72 and 73 ml
E)None of the above.

Answer 3

70.49 and 74.51 ml

Question 4

A producer of specialty products uses a variety of natural and man-made materials to make unique countertops for kitchens and baths.One product line mixes concrete and natural river stone to make countertops that are polished to a high shine revealing unique patterns.Occasionally coarse sand will result in undesirable pitting and rough spots on surfaces.Consequently, as part of its quality control efforts, 8 by 4 foot polished slabs are checked periodically for imperfections.For each slab inspected the number of imperfections (pits, rough spots, etc.) is recorded.If the average number of imperfections per 8 by 4 foot polished slab is 2.6, the control limits for the appropriate control chart are ________________________ .

A)0 and 7.44
B)0.98 and 4.21
C)0 and 9.89
D)1.24 and 3.96
E)None of the above.

Question 5

A paper products manufacturer coats paper with a thin film of wax.To initiate control charting, data are collected on the thickness of the coating (measured in mm) by taking twenty-five samples each of size five.The appropriate control chart for these data is the ________________________ .

A)c chart
B)p chart
C)C_p index
D)x-bar and R chart
E)ARL chart

Question 6

An importer of decorative ceramic tile samples 50 tiles each day from incoming shipments.Some tiles are cracked or broken before or during transit, rendering them useless scrap.Sampling from incoming shipments for 30 days reveals that a total of 250 tiles are cracked or broken.The centerline on the p chart for these data is ________________________ .

A)0.250
B)1.83
C)2.5
D)0.167
E)6.1

Question 7

Which of the following statements is false regarding control charts?

A)If we view using a control chart as a graphical hypothesis test, the null hypothesis is that the process has not changed.
B)A type I error in control charting results in an unnecessary adjustment to the process.
C)A type II error in control charting results in an unnecessary adjustment to the process.
D)A process within which special cause variation is present is said to be out of control.
E)A process which exhibits only common cause variation is said to be in control.

Question 8

In order to achieve higher levels of customer satisfaction, a company initiates monitoring the complaint resolution process of its customer service representatives.As a first step, the company decides to collect data on the number of unanswered calls out of the first 250 incoming calls to its call center made each day.At the end of monitoring 25 days, it was found that a total of 500 incoming calls went unanswered.The control limits for the p-chart of these data are ________________________ .

A)0.029 and 0.131
B)0 and 0.304
C)0.066 and 0.094
D)0.048 and 0.112
E)None of the above.

Question 9

Machine oil is used by clothing manufacturers to lubricate and protect sewing machines.A company that produces machine oil must ensure that the viscosity of its product meets customer requirements.Consequently, the viscosity of every batch of oil produced is measured.Suppose that the process mean is 101 cP and the process standard deviation is 1.50 cP.What are the limits for a runs chart to be used to see that the process remains control?

A)99.5 cP and 102.5 cP
B)96.5 cP and 105.5 cP
C)95.5 cP and 106.5 cP
D)92.5 cP and 110.5 cP
E)None of the above

Question 10

Machine oil is used by clothing manufacturers to lubricate and protect sewing machines.A company that produces machine oil must ensure that the viscosity of its product meets customer requirements.Consequently, the viscosity of every batch of oil produced is measured.Suppose that the process mean is 101 cP and the process standard deviation is 1.50 cP.What type of chart should be used to ensure the process remains in control?

A)p-chart
B)c-chart
C)R-chart
D)Individuals chart
E)ARL chart

Question 11

A company that manufactures health food snacks produces low sodium rice chips.To monitor the process for sodium levels, chips are selected periodically and the amount of sodium (mg) measured.For each of thirty samples consisting of 8 chips, the mean and range in sodium content is determined.The average of the means across all samples is 55 mg and the average range is 2.2 mg.The lower and upper control limits for the R chart are ________________________ .

A)0.2992 and 4.1008 mg.
B)0 and 4.4088 mg.
C)0.136 and 1.864 mg.
D)2.1999 and 30.152 mg.
E)0.2493 and 3.4167 mg.

Question 12

A company that manufactures health food snacks produces low sodium rice chips.To monitor the process for sodium levels, chips are selected periodically and the amount of sodium (mg) measured.For each of thirty samples consisting of 8 chips, the mean and range in sodium content is determined.The average of the means across all samples is 55 mg and the average range is 2.2 mg.The estimated process standard deviation () is ________________________ .

A)0.773 mg.
B)2.683 mg.
C)0.073 mg.
D)16.176 mg.
E)1.833 mg.

Question 13

By design, a required dimension on a part is 0.575 inches plus or minus 0.008 inches.Assume that the process producing this part is stable with a mean of 0.579 inches and standard deviation of 0.002 inches.The specification limits for this part are ________________________ .

A)0.554 to 0.596 inches
B)0.567 to 0.583 inches
C)0.576 to 0.598 inches
D)0.572 to 0.584 inches
E)0.575 to 0.578 inches

Question 14

An automatic filling process is used to dispense hand sanitizer into small purse size bottles.The target weight is 75 ml.The company has initiated control charting to stabilize and improve the automatic filling process.For each of twenty-five samples consisting of four bottles, the contents were measured and the mean weight and range were determined.The average of the means across all samples was found to be 72.5 ml.and the average range was 2.75 ml.The estimate of the process standard deviation is ________________________ .

A)2.75 ml
B)2.44 ml
C)1.88 ml
D)1.34 ml
E)None of the above.

Question 15

An automatic filling process is used to dispense hand sanitizer into small purse size bottles.The target weight is 75 ml.The company has initiated control charting to stabilize and improve the automatic filling process.For each of twenty-five samples consisting of four bottles, the contents were measured and the mean weight and range were determined.The average of the means across all samples was found to be 72.5 ml.and the average range was 2.75 ml.The control limits for the R chart are ________________________ .

A)0 and 4.3566 ml
B)0 and 6.2755 ml
C)0 and 2.8875 ml
D)2.00 and 3.50 ml
E)None of the above.

Question 16

By design, a required dimension on a part is 0.575 inches plus or minus 0.008 inches.Assume that the process producing this part is stable with a mean of 0.579 inches and standard deviation of 0.002 inches.What is the C_p index?

A)1.33
B)2.00
C)0.67
D)1.00
E)None of the above

Question 17

A manufacturer of a particular grade of copper tubing collects data on the number of flaws occurring in 500 foot coils.Suppose they sample a total of 40 coils to initiate control charting.The average number of defects per coil is 2.5.The lower and upper control limits for the appropriate control chart for these data are ________________________ .

A)0 and 7.24
B)0 and 5.66
C)2.24 and 7.24
D)2.24 and 4.08
E)none of the above.

Question 18

A manufacturer of a particular grade of copper tubing collects data on the number of flaws occurring in 500 foot coils.Suppose they sample a total of 40 coils to initiate control charting.The average number of defects per coil is 2.5.The appropriate control chart for these data is the ________________________ .

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

Question 19

A company that manufactures health food snacks produces low sodium rice chips.To monitor the process for sodium levels, chips are selected periodically and the amount of sodium (mg) measured.For each of thirty samples consisting of 8 chips, the mean and range in sodium content is determined.The average of the means across all samples is 55 mg and the average range is 2.2 mg.The lower and upper control limits for the x-bar chart are ________________________ .

A)52.67 and 57.33 mg.
B)51.15 and 58.85 mg.
C)54.18 and 55.82 mg.
D)48.89 and 57.61 mg.
E)37.84 and 72.16 mg.

Question 20

Machine oil is used by clothing manufacturers to lubricate and protect sewing machines.A company that produces machine oil must ensure that the viscosity of its product meets customer requirements.Consequently, the viscosity of every batch of oil produced is measured.Suppose that the process mean is 101 cP and the process standard deviation is 1.50 cP.What is the C_pk index if the customer specifications require viscosity of the machine oil to be 100cP ± 4.5 cP?

A)1.0
B)1.22
C)0.78
D)1.67
E)None of the above