Question 1

If all sample averages on an  -chart fall within the control limits,all output will be conforming.

Accepted Answer

False

Question 2

A histogram of data that resembles the normal distribution indicates that the process is in control.

Accepted Answer

A histogram resembling the normal distribution indicates the distribution of data, but it does not necessarily mean the process is in control. Process control is determined by statistical control charts that assess variation over time, not just the shape of the distribution.

Question 3

If points on a control chart are determined to be the result of special causes,the points should be eliminated and new control limit values should be computed.

Accepted Answer

If points on a control chart are determined to be the result of special causes, it means that they are not representative of the normal process variation and should be eliminated. New control limit values should be computed based on the remaining points that represent the typical process variation.

Question 4

Control limits for variables and attribute data utilize the same mathematical formulas.

Accepted Answer

Control limits for variables data are calculated using standard deviation and mean, while control limits for attribute data are based on proportions or counts, using different statistical methods.

Question 5

The most commonly applied control limits for variables data are 3-sigma control limits.

Accepted Answer

3-sigma control limits are the most commonly used control limits for variables data, which represents 99.73% of the data falling within the limits.

Question 6

The centerline for the np-chart is equal to the average number of nonconforming items per sample.

Accepted Answer

The centerline for the np-chart is indeed equal to the average number of nonconforming items per sample.

Question 7

A "hugging the centerline limit" pattern in a control chart can be the result of using two different lots of material in one process.

Accepted Answer

The answer of A "hugging the centerline limit" pattern in...

Question 8

If all the points on a control chart are within the control limits,then the process is in statistical control.

Accepted Answer

The answer of If all the points on a control...

Question 9

For variables data,the necessary sample size can be estimated by specifying the desired minimum shift in the process mean to be detected.

Accepted Answer

This is correct. The minimum detectable shift is typically determined by the desired statistical power and the level of detection that is deemed important for the process being studied. The necessary sample size is then calculated based on these factors.

Question 10

Assignable causes are more difficult to identify in unstable processes.

Accepted Answer

Unstable processes have a large amount of natural variation, making it challenging to separate assignable causes from random variation.

Question 11

Attribute control charts require larger sample sizes than variable control charts.

Accepted Answer

Attribute control charts involve counting the number of defective units in a sample, while variable control charts measure the actual values of a characteristic. Since attribute charts are based on discrete data, they require larger sample sizes to ensure statistical validity and accuracy. Variable control charts, on the other hand, can often use smaller sample sizes since they are based on continuous data.

Question 12

A p-chart is used with attribute data.

Accepted Answer

A p-chart is used to monitor the proportion of defects or non-conformities in a sample over time. It is a type of control chart that is used with attribute data, which involves counting the number of occurrences or non-occurrences of a particular characteristic or attribute within a sample.

Question 13

Common and special causes must be eliminated before process capability can be determined.

Accepted Answer

Process capability is determined by analyzing the inherent variability of a process, which is primarily affected by common causes. Special causes are external and should be addressed separately to stabilize the process before assessing capability.

Question 14

Variation in process output can occur as a result of chance or as a result of assignable causes.

Accepted Answer

Variation in process output can be classified as either common cause variation or special cause variation. Common cause variation, also known as chance cause variation, refers to the natural variability that is inherent in a process. It is caused by factors that are inherent in the process itself and is expected to occur over time. Special cause variation, also known as assignable cause variation, refers to variation that is caused by factors that are not inherent to the process. These causes can be identified and addressed in order to improve the process.

Question 15

Histograms allow you to distinguish between common and special causes of variation.

Accepted Answer

Histograms are used to visualize the distribution of a dataset and can help identify the shape, central tendency, and spread of the data, but they do not inherently distinguish between common and special causes of variation. Control charts are the tools typically used for identifying common and special causes of variation in a process.

Question 16

A c-chart is more appropriate than a u-chart if the nature of the process does not yield discrete measurable units of output.

Accepted Answer

A c-chart is used for monitoring the count of defects in a fixed sample size, while a u-chart is used when the sample size varies and measures defects per unit. If the process does not yield discrete measurable units, neither chart would be appropriate.

Question 17

If the cost of investigating the cause of an apparent out-of-control situation is high,narrower control limits should be adopted.

Accepted Answer

Narrower control limits increase the likelihood of false alarms, leading to more investigations. If investigation costs are high, it is better to maintain standard control limits to avoid unnecessary investigations.

Question 18

Process capability indices cannot be computed from data in an  -chart.

Accepted Answer

The answer of Process capability indices cannot be computed from...

Question 19

The assumption of normality of observations is more critical fo  -charts than for x-charts.

Accepted Answer

The answer of The assumption of normality of observations is...

Question 20

If the cost of a Type II error is low,narrower control limits should be selected.

Accepted Answer

If the cost of a Type II error is low, it means that we can tolerate a higher likelihood of accepting a false null hypothesis. In this case, we can use narrower control limits to increase the sensitivity of our process and detect smaller deviations from the mean. This will reduce the risk of a Type I error but may increase the risk of a Type II error, which is acceptable if its cost is low.

Quiz 13: Statistical Process Control

If all sample averages on an -chart fall within the control limits,all output will be conforming.