Control Charts for Attributes: Monitoring and Controlling Discrete Data Processes

Question 1

Which of the following is the primary purpose of using a p-chart?

Accepted Answer

To monitor and control processes with discrete data, such as the proportion of nonconforming items in a sample.

Answer

To monitor and control processes with continuous data, such as the weight of individual units in a production run.

Answer

To identify specific assignable causes of variation in a process.

Answer

To determine the capability of a process, such as its ability to meet customer specifications.

Question 2

What is the key difference between a p-chart and a c-chart?

Accepted Answer

P-charts are used to monitor the proportion of nonconforming items, while c-charts are used to monitor the number of nonconforming items.

Answer

C-charts are used to monitor the proportion of nonconforming items, while p-charts are used to monitor the number of nonconforming items.

Answer

Both p-charts and c-charts are used to monitor the proportion of nonconforming items.

Answer

There is no difference between a p-chart and a c-chart.

Question 3

Which of the following is considered a common cause of variation in a process?

Accepted Answer

Normal process variation due to inherent randomness.

Answer

Equipment failure

Answer

Operator error

Answer

Changes in raw materials

Question 4

When an out-of-control signal is detected on a control chart, what is the most appropriate initial action to take?

Accepted Answer

Investigate the process to determine the root cause of the variation.

Answer

Increase the sample size to make the control limits wider.

Answer

Decrease the control limits to make them more sensitive.

Answer

Ignore the signal and continue monitoring the process.

Question 5

Is the statement 'Control charts are only useful for monitoring manufacturing processes' true or false?

Accepted Answer

False

Answer

True

Question 6

Which of the following is NOT a common type of control chart for attributes?

Accepted Answer

R-chart

Answer

p-chart

Answer

c-chart

Answer

np-chart

Question 7

The central line of a p-chart represents the:

Accepted Answer

Average proportion of defective items in the population

Answer

Maximum allowable proportion of defective items

Answer

Minimum allowable proportion of defective items

Answer

Standard deviation of the proportion of defective items

Question 8

A c-chart is used to monitor:

Accepted Answer

The number of defects per unit

Answer

The proportion of defective units

Answer

The average number of defects per unit

Answer

The standard deviation of the number of defects per unit

Question 9

What is the purpose of the UCL and LCL on a control chart?

Accepted Answer

To set limits for acceptable variation

Answer

To identify if the process is within control

Answer

To determine the average value of the process

Answer

To calculate the standard deviation of the process

Question 10

What is the difference between a p-chart and a np-chart?

Accepted Answer

p-chart is for proportions, np-chart is for counts

Answer

np-chart is for proportions, p-chart is for counts

Answer

p-chart is for attributes, np-chart is for variables

Answer

np-chart is for attributes, p-chart is for variables

Question 11

Which of the following is NOT an advantage of using control charts?

Accepted Answer

Elimination of all process variation

Answer

Early detection of process shifts

Answer

Increased process stability

Answer

Reduced scrap and rework

Question 12

What is the primary purpose of a quality control chart?

Accepted Answer

To identify process variability

Answer

To determine the process mean

Answer

To set process limits

Answer

To improve product quality

Question 13

The purpose of a p-chart is to monitor:

Accepted Answer

The proportion of nonconforming units in a sample

Answer

The number of defects per unit

Answer

The average value of a measurement

Answer

The variance of a measurement

Question 14

The center line of a p-chart is calculated as:

Accepted Answer

The average proportion of nonconforming units in the process

Answer

The target proportion of nonconforming units in the process

Answer

The standard deviation of the proportion of nonconforming units in the process

Answer

The upper control limit of the process

Question 15

An out-of-control point on a p-chart indicates that:

Accepted Answer

The proportion of nonconforming units in the process has significantly changed

Answer

The process is stable and predictable

Answer

The data is not reliable and should be discarded

Answer

The sample size is too small to be statistically significant

Question 16

According to control chart conventions, a process is considered out-of-control when:

Accepted Answer

Three points fall outside the control limits

Answer

One point falls outside the control limits

Answer

Two points fall outside the control limits

Answer

Four points fall outside the control limits

Question 17

To ensure accurate process monitoring, why is it essential to establish process stability before implementing attribute control charts?

Accepted Answer

Prevent false alarms

Answer

Enhance process capability

Answer

Reduce production expenses

Question 18

Which type of control chart is designed to monitor the proportion of nonconforming items in a sample?

Accepted Answer

p-chart

Answer

c-chart

Answer

u-chart

Answer

x-bar chart

Question 19

What does a large sample size on a p-chart generally indicate?

Accepted Answer

The process is more stable and reliable

Answer

The process is less stable and reliable

Answer

The process has a higher proportion of nonconforming items

Answer

The process has a lower proportion of nonconforming items

Question 20

What is the key difference between a p-chart and a c-chart?

Accepted Answer

A p-chart monitors proportions or percentages, while a c-chart monitors counts or frequencies

Answer

A c-chart monitors proportions or percentages, while a p-chart monitors counts or frequencies

Answer

Both charts monitor proportions or percentages

Answer

Both charts monitor counts or frequencies

Question 21

What is the primary purpose of the upper control limit (UCL) and lower control limit (LCL) on a control chart?

Accepted Answer

To indicate when the process is out of control

Answer

To define the acceptable range of variation for the process

Answer

To set the target value or desired state for the process

Answer

To show the historical range of data values

Question 22

To ensure the validity of control limits and the center line in an attribute control chart, which method should be employed?

Accepted Answer

Compare the chart's pattern to expected distributions.

Answer

Apply industry-standard limits without further verification.

Answer

Ignore control limits and focus solely on data points.

Question 23

When is it appropriate to use a c-chart instead of a p-chart?

Accepted Answer

When monitoring processes with a constant number of defects per unit

Answer

When the sample size is small

Answer

When the process produces both conforming and non-conforming units

Answer

When the data is non-normally distributed

Question 24

Which of the following is NOT a type of control limit used in control charts?

Accepted Answer

Guideline limit

Answer

Upper control limit (UCL)

Answer

Lower control limit (LCL)

Answer

Action limit

Question 25

What does a point falling outside the control limits on a control chart indicate?

Accepted Answer

A potential indication of a special cause of variation

Answer

A normal occurrence within the expected process variation

Answer

A warning that the process is approaching but not yet out of control

Answer

Confirmation that the process is in control

Question 26

What is the fundamental difference between a variable control chart and an attribute control chart?

Accepted Answer

Variable control charts are used for continuous data, while attribute control charts are used for discrete data

Answer

Attribute control charts are more sensitive than variable control charts

Answer

Variable control charts require a larger sample size than attribute control charts

Answer

Attribute control charts are more difficult to interpret than variable control charts

Question 27

In a p-chart, what does the np value represent?

Accepted Answer

The total number of units inspected

Answer

The number of non-defective units

Answer

The number of defective units

Answer

The proportion of defective units

Question 28

When should you utilize a p-chart instead of a c-chart for quality control?

Accepted Answer

When the data involves the proportion of non-conforming items in a sample

Answer

When the data involves the count of non-conforming items in a sample

Answer

When the process is stable and predictable

Answer

When the process is highly variable and unstable

Question 29

Given a p-chart with an average proportion of 0.05 and a standard deviation of 0.02, what are the control limits?

Accepted Answer

UCL = 0.11, LCL = 0.03

Answer

UCL = 0.09, LCL = 0.01

Answer

UCL = 0.13, LCL = 0.05

Answer

UCL = 0.15, LCL = 0.07

Question 30

Which of the following is NOT a potential benefit of implementing control charts for attributes?

Accepted Answer

Complete elimination of all process variation

Answer

Early detection of process shifts

Answer

Identification of assignable causes of variation

Answer

Documentation of process stability over time

Question 31

When interpreting a p-chart, what does a data point located above the upper control limit indicate?

Accepted Answer

The process is likely out of control due to assignable causes

Answer

The process is stable but operating close to the control limit

Answer

The process is operating normally within expected variation

Answer

The control chart is invalid and should be disregarded

Question 32

In a manufacturing process where the number of defects per item is relatively high, which type of control chart would be more appropriate?

Accepted Answer

c-chart

Answer

p-chart

Answer

Both p-chart and c-chart

Answer

Neither p-chart nor c-chart

Question 33

Which of the following best describes the primary purpose of a p-chart?

Accepted Answer

To monitor the proportion of nonconforming items within a sample

Answer

To monitor the total number of nonconforming items within a sample

Answer

To monitor the average number of nonconforming items within a sample

Question 34

Which formula is used to calculate the control limits for a p-chart?

Accepted Answer

UCL = p + 3√(p(1-p)/n) and LCL = p - 3√(p(1-p)/n)

Answer

UCL = p + 4√(p(1-p)/n) and LCL = p - 4√(p(1-p)/n)

Answer

UCL = p + 3√(np(1-p)) and LCL = p - 3√(np(1-p))

Question 35

Which of the following formulas is used to calculate the control limits for a c-chart?

Accepted Answer

UCL = c + 3√(c) and LCL = c - 3√(c)

Answer

UCL = c + 4√(c) and LCL = c - 4√(c)

Answer

UCL = c + √(c) and LCL = c - √(c)

Answer

UCL = c + 2√(c) and LCL = c - 2√(c)

Question 36

What is the typical implication of a data point falling outside the control limits on a control chart?

Accepted Answer

The process may not be stable and further investigation is likely necessary

Answer

The process is slightly out of control but can be corrected through minor adjustments

Answer

The process is stable, and no action is required

Question 37

What is the primary purpose of using subgroups in control charting?

Accepted Answer

To reduce the impact of individual observations on the control chart

Answer

To increase the sample size

Answer

To make the control chart easier to read

Question 38

Which of the following is not a limitation of using control charts?

Accepted Answer

They can be used to predict future process performance

Answer

They are susceptible to non-random variation

Answer

They can be challenging to interpret

Answer

They require substantial data to be useful

Question 39

What is a key distinction between special cause and common cause variation?

Accepted Answer

Special cause variation is caused by identifiable factors, while common cause variation is inherent to the process

Answer

Special cause variation is random, while common cause variation is non-random

Question 40

Which of the following is not typically considered a benefit of using control charts?

Accepted Answer

They are infallible and never generate false positives

Answer

They can improve process stability

Answer

They can help reduce waste

Question 41

Which type of control chart for attributes is used when the data being monitored consists of proportions or percentages?

Accepted Answer

p-chart

Answer

u-chart

Answer

c-chart

Question 42

What does the center line on a control chart represent?

Accepted Answer

The average value of the process being monitored

Answer

The desired value of the process

Answer

The range of acceptable variation

Answer

The upper control limit

Question 43

Which of the following is a type of control chart for attributes designed to monitor the number of defects per unit?

Accepted Answer

c-chart

Answer

R-chart

Answer

s-chart

Question 44

What is the primary objective of using control charts for attributes?

Accepted Answer

Detecting and eliminating assignable causes of variation

Answer

Adjusting process settings to optimize quality

Answer

Predicting future process behavior

Question 45

What is the purpose of the upper control limit (UCL) and lower control limit (LCL) on a control chart?

Accepted Answer

Establishing the acceptable range of variation for the process

Answer

Setting the target value for the process

Answer

Indicating the average and standard deviation of the process

Answer

Identifying potential problems with the process

Question 46

What is the first step in the process of creating a control chart for attributes?

Accepted Answer

Collecting data from the process

Answer

Determining the control limits

Answer

Plotting the data on a graph

Question 47

What is the main difference between a p-chart and a c-chart?

Accepted Answer

The type of data they monitor: proportions/percentages (p-chart) vs counts (c-chart)

Answer

The control limits they use

Answer

The way they are constructed

Answer

The interpretation of their patterns

Question 48

Which type of control chart is employed to monitor the proportion of defective items in a sample?

Accepted Answer

p-chart

Answer

x-bar chart

Answer

c-chart

Answer

s-chart

Question 49

What is the primary purpose of a control limit on a control chart?

Accepted Answer

To establish boundaries indicating when a process is considered unstable

Answer

To represent the desired target value

Answer

To guide adjustments in process parameters

Question 50

What is the most crucial factor to consider when determining the sample size for a control chart?

Accepted Answer

Anticipated proportion of defective items in the process

Answer

The cost associated with sampling

Answer

The time required for inspection

Question 51

Which type of control chart is designed to monitor the count of defective items in a sample?

Accepted Answer

c-chart

Answer

x-bar chart

Answer

p-chart

Answer

s-chart

Question 52

Which of the following is NOT a potential benefit of utilizing control charts?

Accepted Answer

Reduced production time

Answer

Enhanced product quality

Answer

Early detection of process variations

Answer

Increased process stability

Question 53

What does a sequence of data points falling above or below the average on a control chart indicate?

Accepted Answer

Potential process instability

Answer

Minimal process variation

Answer

Normal distribution

Answer

Process stability

Question 54

Which of the following is NOT a valid reason for investigating a data point outside the control limits on a control chart?

Accepted Answer

Inherent randomness

Answer

Operator error

Answer

Machine malfunction

Answer

Supplier quality issue

Question 55

What is the distinction between a Type I and Type II error in control chart analysis?

Accepted Answer

Type I: false positive, Type II: false negative

Answer

Type I: false negative, Type II: false positive

Answer

Type I: major error, Type II: minor error

Question 56

Which type of control chart is most appropriate for monitoring processes with infrequent defects?

Accepted Answer

c-chart

Answer

x-bar chart

Answer

p-chart

Answer

s-chart