Question 1

Which of the following quality control sample statistics measures a quality characteristic which is an attribute?

Accepted Answer

Proportion is the measure of the presence of a quality characteristic which is an attribute. The other statistics (mean, variance, standard deviation, and range) are used for measuring quality characteristics which are variables.

Question 2

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

Accepted Answer

The R-chart is used to monitor the process variability, particularly the dispersion or spread of the data. Therefore, it is most likely to detect a change in process variability.

Question 3

Which statement is an accurate description of a process that is "capable"?

Accepted Answer

A process that is "capable" means that its variability (i.e. the spread of values it produces) is within the allowable variation specified by its design specifications. This means that statement C, which describes a process with variability less than the variation allowed by design specifications, is the accurate description of a "capable" process.

Question 4

Studies on a bottle-filling machine indicates it fills bottles to a mean of 16 ounces with a standard deviation of 0.10 ounces.Assuming the Cpindex = 1.0,what is/are the process specification(s)?

Accepted Answer

The answer of Studies on a bottle-filling machine indicates it...

Question 5

The six sigma quality improvement methodology is called:

Accepted Answer

The Six Sigma quality improvement methodology is called DMAIC, which stands for Define, Measure, Analyze, Improve, and Control. The PDSA (Plan-Do-Study-Act) cycle is used in other quality improvement methodologies, such as Lean and Total Quality Management. 5W2H and continuous improvement system are not specific to Six Sigma.

Question 6

A c-chart is used for:

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.

Question 7

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

Accepted Answer

A c-chart is specifically designed to monitor the number of defects per unit, making it the best choice for this scenario. P-chart is used to monitor the proportion of defects in a sample, R-chart is used to monitor the range of values in a sample, x-bar chart is used to monitor the process mean. Gantt chart is used for project management, not quality control.

Question 8

Using three sigma control limits (rather than two sigma limits)tends to have what impact on error probabilities?

Accepted Answer

Using three sigma control limits, compared to two sigma limits, increases the threshold for identifying a process as out of control. This means it's less likely to flag a process as out of control when it's actually in control (reducing Type I errors, which are false positives), but it also makes it more likely to miss an out-of-control process (increasing Type II errors, which are false negatives).

Question 9

A point that plots below the lower control limit on the range chart:

Accepted Answer

A point plotting below the lower control limit on a range chart may indicate that the process variation has decreased, which could be a sign of an improvement in process consistency.

Question 10

A control chart used to monitor the fraction of defectives generated by a process is the:

Accepted Answer

A control chart used to monitor the fraction of defectives generated by a process is the p-chart. The p-chart plots the proportion of defective items in each sample, making it suitable for monitoring processes where the number of items produced is constant. The R-chart is used to monitor the range or variation in a process, the x-bar chart is used to monitor the central tendency or average of a process, the c-chart is used to monitor the number of defects per unit, and the Gantt chart is used for project scheduling and management.

Question 11

A control chart used to monitor the process mean is the:

Accepted Answer

The x-bar chart is used to monitor the process mean, making it the appropriate choice for this question. The p-chart is used to monitor the proportion of nonconforming items in a sample, the R-chart is used to monitor the process variability, the c-chart is used to monitor the number of defects (when the sample size is constant), and the Gantt chart is used for project management scheduling.

Question 12

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

Accepted Answer

A point outside of the lower control limit on an R-chart indicates that the process variation is higher than expected or desired. This means that the methods and processes used in the production should be investigated for potential improvements. Therefore, it is important to investigate such a point instead of ignoring or assuming no process variation.

Question 13

Which of the following is not needed to calculate sample mean control charts?

Accepted Answer

The sample range is not needed to calculate sample mean control charts. The choice for z, the standard deviation of the sampling distribution, and the average of sample means (grand mean) are all required.

Question 14

The term "2 sigma limits" in the context of a control chart refers to the variability of the:

Accepted Answer

2 sigma limits in a control chart refer to the variability of the sampling distribution, which is used to determine control limits based on the standard deviation of the sample means.

Question 15

When using control charts sample size is important.Smaller samples are more likely to reveal a process change because a change is more likely to take place ______ the large sample,rather than ________ small samples.

Accepted Answer

Smaller samples are more sensitive to changes because a change is more likely to occur within the range of a large sample, rather than between smaller samples. This means that variations or shifts in the process are easier to detect with smaller samples, as the impact of any change is more pronounced.

Question 16

The DMAIC methodology involves all EXCEPT which of the following?

Accepted Answer

The DMAIC methodology involves five stages: define, measure, analyze, improve, and control. "Model" is not one of the stages.

Question 17

The probability of concluding that an assignable variation exists when only random variation is present is:

Accepted Answer

Type I error is the probability of concluding that there is a significant difference or assignable cause when in fact there is only random variation present.

Question 18

For which of the following would a p-chart be used?

Accepted Answer

A p-chart is used to monitor the proportion of defectives in a sample, making it the best choice among the given options. A p-chart is a type of control chart that is used to track the number or proportion of nonconforming units in a sample. It is an effective tool for monitoring processes and detecting any deviations from the expected performance.

Question 19

When a process is judged out of control for an important character?istic,what corrective action should be taken?

Accepted Answer

When a process is judged out of control for an important characteristic, stopping the process and taking corrective action is necessary to prevent further production of non-conforming products.

Question 20

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

Accepted Answer

An x-bar chart is used to monitor changes in the process mean over time. A shift in the process mean will cause the x-bar chart to show out-of-control signals or points beyond the control limits. The p-chart is used to monitor proportion non-conforming data, c-chart is used to monitor count non-conforming data, R-chart is used to monitor the variability of the process, and the s-chart is used to monitor the standard deviation of the process.

Quiz 15: Statistical Quality Control