Question 1

Four samples of three observations each have been taken, with actual measurements (in centimeters) shown below.Construct three-sigma mean and range charts.

Accepted Answer

The answer of Four samples of three observations each have...

Question 2

A point which is outside of the lower control limit on an R-chart:
A)is an indication that no cause of variation is present
B)should be ignored because it signifies better than average quality
C)should be investigated because an assignable cause of variation might be present
D)should be ignored unless another point is outside that limit
E)is impossible since the lower limit is always zero

Accepted Answer

Points outside of the control limits indicate that there may be an assignable cause of variation present. Therefore, it should be investigated. A and B are not correct as they do not acknowledge the potential issue indicated by the out-of-control point. D is not correct as the single point outside the limit should still be investigated. E is not correct as the lower limit is not always zero, and the question does not imply that it is.

Question 3

If a process is performing as it should, it is still possible to obtain observations which are outside of which limits? (I) tolerances
(II) control limits
(III) process variability
A)I
B)II
C)I and II
D)II and III
E)I, II, and III

Accepted Answer

The answer of If a process is performing as it...

Question 4

Perform run tests on the given data.What can you conclude?

Accepted Answer

The answer of Perform run tests on the given data.What...

Question 5

The process capability index (Cpk) may mislead if: (I) the process is not stable.
(II) the process output is not normally distributed.
(III) the process is not centered.
A)I and II
B)I and III
C)II and III
D)II only
E)I, II and III

Accepted Answer

The answer of The process capability index (Cpk) may mislead...

Question 6

A c-chart is used for:
A)means
B)ranges
C)percent defective
D)fraction defective per unit
E)number of defects per unit

Accepted Answer

A c-chart is used for monitoring the number of defects per unit in a process. It is applicable when the number of opportunities for defects is constant and known for each sample.

Question 7

The purpose of control charts is to:
A)estimate the proportion of output that is acceptable
B)weed out defective items
C)determine if the output is within tolerances/specifications
D)distinguish between random variation and assignable variation in the process
E)provide meaningful work for quality inspectors

Accepted Answer

The answer of The purpose of control charts is to:
A)estimate...

Question 8

A process that makes chocolate candy bars has an output that is normally distributed with a mean of 6 oz.and a standard deviation of .01 oz.A job is to be run that requires 200 candy bars.
Determine three sigma control limits for an x-bar chart assuming a sample size of 10.
If specifications are 5.98 to 6.02, what run size should be used for this job so that the expected number of good candy bars is 200, assuming the process is in control?

Accepted Answer

The answer of A process that makes chocolate candy bars...

Question 9

A plot below the lower control limit on the range chart: (I) should be ignored since lower variation is desirable
(II) may be an indication that process variation has decreased
(III) should be investigated for assignable cause
A)I and II
B)I and III
C)II and III
D)II only
E)I, II, and III

Accepted Answer

A plot below the lower control limit on the range chart indicates a decrease in process variation, which could be due to an assignable cause. It's not something to be ignored as it might signify an improvement or an issue that needs to be understood and possibly standardized.

Question 10

A town's department of public works is concerned about adverse public reaction to a sewer project that is currently in progress.Because of this, the Commissioner of Public Works has authorized a weekly survey to be conducted of town residents.Each week, a sample of 100 residents is questioned on their feelings towards the project.The results to date are shown below.Analyze this data using control charts that would provide for a 5% risk of Type I error.

Accepted Answer

The answer of A town's department of public works is...

Question 11

Construct the appropriate two-sigma control chart for the sample observations listed below.

Accepted Answer

The answer of Construct the appropriate two-sigma control chart for...

Question 12

The optimum level of inspection is where the:
A)cost of inspection is minimum
B)cost of passing defectives is minimum
C)total cost of inspection and defectives is maximum
D)total cost of inspection and defectives is minimum
E)difference between inspection and defectives costs is minimum

Accepted Answer

The optimum level of inspection is where the total cost of inspection and defectives is minimum. This means finding the balance between the cost of inspection and the cost of defectives. By minimizing the total cost of both factors, the company can achieve the most cost-effective solution for their inspection process.

Question 13

_______ variation is a variation whose cause can be identified.
A)Assignable
B)Controllable
C)Random
D)Statistical
E)Theoretical

Accepted Answer

Assignable variation is caused by identifiable factors that can be controlled, whereas random variation occurs spontaneously and cannot be controlled. Controllable variation is similar to assignable variation, but implies that the variation can be prevented or eliminated altogether through a change in the process. Statistical and theoretical variations are not common terminology in quality control.

Question 14

Which of the following relationships must always be incorrect? A)Tolerances > process variability > control limits B)Process variability > tolerances > control limits C)Tolerances > control limits > process variability D)Process variability > control limits > tolerances E)Process variability

Accepted Answer

Tolerances represent the acceptable range of variability for a product or process, while control limits represent the range of variability that is expected to occur within a process. Process variability is the actual range of variability observed in a process. Tolerances should be wider than control limits, as they represent the acceptable range of variability for the product. However, process variability can be larger than control limits, indicating that the process is out of control and requires corrective action. Option C, where tolerances are greater than the control limits, goes against this logic and is therefore incorrect.

Question 15

The range chart (R-chart) is most likely to detect a change in:
A)proportion
B)mean
C)number defective
D)variability
E)sample size

Accepted Answer

The R-chart is used to monitor variability in a process. Therefore, it is most likely to detect a change in variability (choice D). The other options do not relate to the R-chart.

Question 16

A time-ordered plot of sample statistics is called a(n) ______ chart.
A)Statistical
B)Inspection
C)Control
D)SIMO
E)Limit

Accepted Answer

A time-ordered plot of sample statistics is commonly called a control chart, which is used to monitor a process over time for any shifts or changes in performance. The chart helps to identify when a process is out of control, allowing for corrective action to be taken. Control charts typically include upper and lower control limits to help determine whether a process is in control and meeting defined standards.

Question 17

The probability of concluding that assignable variation exists when only random variation is present is: (I) the probability of a Type I error
(II) known as the alpha risk
(III) highly unlikely
(IV) the sum of probabilities in the two tails of the normal distribution
A)I and II
B)I and IV
C)II and III
D)I, II, and IV
E)I, III, and IV

Accepted Answer

The probability of concluding that assignable variation exists when only random variation is present is the probability of a Type I error (I) and is known as the alpha risk (II). It is also represented by the sum of probabilities in the two tails of the normal distribution (IV), which are the critical regions for rejecting the null hypothesis when it is actually true.

Question 18

A control chart used to monitor the number of defects per unit is the:
A)p-chart
B)R-chart
C)x-bar chart
D)c-chart
E)Gantt chart

Accepted Answer

A c-chart is used to monitor the number of defects per unit. The other control charts listed are used for different types of quality control monitoring, such as controlling the proportion of defective units (p-chart), the range of measurements (R-chart), the average measurement of a process (x-bar chart), and scheduling and tracking project activities (Gantt chart).

Question 19

A shift in the process mean for a measured characteristic would most likely be detected by a:
A)p-chart 
B)x-bar chart
C)c-chart
D)R-chart
E)s-chart

Accepted Answer

An x-bar chart is used to monitor the process mean. A shift in the process mean would be detected by an x-bar chart.

Question 20

Which of the following is not a step in the quality control process?
A)define what is to be controlled
B)compare measurements to a standard
C)eliminate each of the defects as they are identified
D)take corrective action if necessary
E)evaluate corrective action

Accepted Answer

Eliminating defects as they are identified is a step in the quality assurance process, not the quality control process. The steps in the quality control process are: Define what is to be controlled, measure the process or product, compare the measurements to a standard, take corrective action if necessary, and evaluate the corrective action.

Quiz 10: Quality Control

Four samples of three observations each have been taken, with actual measurements (in centimeters) shown below.Construct three-sigma mean and range charts.

A point which is outside of the lower control limit on an R-chart:

If a process is performing as it should, it is still possible to obtain observations which are outside of which limits? (I) tolerances (II) control limits (III) process variability

Perform run tests on the given data.What can you conclude?

The process capability index (Cpk) may mislead if: (I) the process is not stable. (II) the process output is not normally distributed. (III) the process is not centered.

A c-chart is used for:

The purpose of control charts is to:

A plot below the lower control limit on the range chart: (I) should be ignored since lower variation is desirable (II) may be an indication that process variation has decreased (III) should be investigated for assignable cause

Construct the appropriate two-sigma control chart for the sample observations listed below.

The optimum level of inspection is where the:

_______ variation is a variation whose cause can be identified.

Which of the following relationships must always be incorrect?

The range chart (R-chart) is most likely to detect a change in:

A time-ordered plot of sample statistics is called a(n) ______ chart.

The probability of concluding that assignable variation exists when only random variation is present is: (I) the probability of a Type I error (II) known as the alpha risk (III) highly unlikely (IV) the sum of probabilities in the two tails of the normal distribution

A control chart used to monitor the number of defects per unit is the:

A shift in the process mean for a measured characteristic would most likely be detected by a:

Which of the following is not a step in the quality control process?