Question 1

A control chart that is used when the output of a production process is measured in terms of the proportion defective is
A)a p chart
B)an x-bar chart
C)an R chart
D)an np chart

Accepted Answer

The p chart is used to monitor the proportion defective in a production process. It is used when the sample size is constant and the output is measured in terms of the number of defectives or nonconformities in a sample. The p chart is useful for detecting changes in the process that affect the proportion of defectives, and it is commonly used in quality control applications. The other options, x-bar chart, R chart, and np chart, are used for monitoring variables data, such as process mean, process variability, and number of defects, respectively.

Question 2

Normal or natural variation in the quality of production output that is due purely to chance is called
A)common-cause variation
B)assignable-cause variation
C)control-cause variation
D)correctable-cause variation

Accepted Answer

Common-cause variation is a result of random, naturally occurring variability in a production process. It cannot be traced back to any specific cause or factor and is expected to occur within the normal operating range of a process. The other answer choices refer to variations that have specific, identifiable causes that can be corrected or controlled.

Question 3

The sample result plotted on an np control chart is A)n_p B)np C)the number of perfect units in the sample D)the number of defective units in the sample

Accepted Answer

The np chart is used for monitoring the number of defective items in a sample, so the sample result plotted on an np control chart would be the number of defective units in the sample. Therefore, the best choice is D.

Question 4

A control chart that is used to monitor the range of the measurements in a sample is
A)a p chart
B)an x-bar chart
C)an R chart
D)an np chart

Accepted Answer

An R chart is used to monitor the range of the measurements in a sample. This chart plots the range of the measurements for each subgroup in the sample over time, allowing for detection of any out-of-control situations that may be affecting the variation in the process being monitored. The other control charts listed (p, x-bar, and np charts) are used for different types of data and measurements.

Question 5

Quality assurance consists of
A)quality control
B)quality engineering
C)quality assurance
D)Both quality control and quality engineering are correct.

Accepted Answer

Quality assurance includes both quality control, which focuses on detecting and correcting defects in products, and quality engineering, which involves designing and implementing systems to ensure quality in all stages of production. Therefore, both choices are correct.

Question 6

A control chart used when the output of a process is measured in terms of the mean value of a variable such as a length, weight, temperature, and so on is
A)a p chart
B)an x-bar chart
C)an R chart
D)an np chart

Accepted Answer

The x-bar chart is used to monitor the mean value of a variable over time. It is effective in detecting shifts or trends in the process mean. The p chart (A) is used for proportions, the R chart (C) is used for monitoring the variability of a process, and the np chart (D) is used for monitoring the number of defective items in a sample.

Question 7

Variation in the quality of production output that is due to factors such as machine tools wearing out is called
A)common-cause variation
B)assignable-cause variation
C)acceptable-cause variation
D)natural-cause variation

Accepted Answer

Assignable-cause variation refers to variations in quality that can be traced back to specific causes, such as a worn-out machine tool. This is in contrast to common-cause variation, which is inherent in the process and cannot be attributed to a specific cause. Acceptable-cause variation and natural-cause variation are not industry-standard terms for variations in production output quality.

Question 8

A control chart that is used to monitor the number of defectives in a sample is
A)a p chart
B)an x-bar chart
C)an R chart
D)an np chart

Accepted Answer

An np chart is used to monitor the number of defectives in a sample, where "n" represents the sample size and "p" represents the proportion of defectives in the population. This chart is appropriate when the sample size is constant and the proportion of defectives in the population is low (less than 10%).

Question 9

If the value of c in a single-stage acceptance sampling plan is increased, with n remaining constant, the probability of accepting the lot
A)increases
B)decreases
C)remains the same
D)might increase or decrease, depending on the percent defective in the lot

Accepted Answer

Increasing the value of c (the acceptance number) in a single-stage acceptance sampling plan means that a larger number of defects are allowed before rejecting the lot, thus increasing the probability of accepting the lot.

Question 10

The entire system of policies, procedures, and guidelines established by an organization to achieve and maintain quality is called
A)quality control
B)quality engineering
C)quality assurance
D)Both quality control and quality engineering are correct.

Accepted Answer

Quality assurance encompasses the entire system of policies, procedures, and guidelines established by an organization to achieve and maintain quality. Quality control refers to the specific activities that are performed to verify that a product or service meets established quality standards, while quality engineering involves designing and improving processes to ensure that quality is built into products and services from the beginning.

Question 11

An operating characteristic curve is based on a ________ probability distribution.
A)normal
B)exponential
C)binomial
D)uniform

Accepted Answer

An operating characteristic curve is based on the binomial probability distribution, which is used for binary outcomes like pass/fail, good/bad, or success/failure. The curve plots the probability of accepting a lot with a certain percentage of defective items against the percentage of defective items in the lot. This helps to determine the optimal sample size and acceptance criteria for a particular quality control process. While other probability distributions like normal, exponential, or uniform may be used in other statistical analysis, they are not as directly relevant to operating characteristic curves in the context of quality control.

Question 12

Control charts that are based on data indicating the presence of a defect or the number of defects are called ______ control charts.
A)attributes
B)variables
C)common-cause
D)assignable-cause

Accepted Answer

Attributes control charts are based on data indicating the presence or absence of a defect, whereas variables control charts are based on data indicating the measurement of a characteristic. Common-cause and assignable-cause refer to the sources of variation in a process, not the type of control chart being used.

Question 13

Which of the following is not a type of a control chart?
A)a p chart
B)an x-bar chart
C)an R chart
D)All of these are types of control charts.

Accepted Answer

All of these options are types of control charts commonly used in statistical process control.

Question 14

__________ consist(s) of making a series of inspections and measurements to determine whether quality standards are being met.
A)Quality control
B)Quality engineering
C)Quality assurance
D)Both quality control and quality engineering are correct.

Accepted Answer

Quality control specifically involves inspecting and measuring products or services to ensure they meet quality standards, whereas quality engineering focuses on designing and implementing systems to prevent quality problems from occurring in the first place. Quality assurance encompasses both quality control and quality engineering, but refers more broadly to a company-wide commitment to producing high-quality products or services.

Question 15

The control limits for a p chart are how many standard deviations above and below the proportion defective?
A)one
B)two
C)three
D)four

Accepted Answer

The control limits for a p chart are typically set at three standard deviations above and below the proportion defective to monitor the process variability and control.

Question 16

The control limits for an x-bar chart are how many standard deviations above and below the process mean?
A)one
B)two
C)three
D)four

Accepted Answer

The control limits for an x-bar chart are typically set at three standard deviations above and below the process mean. This is based on the principle that for a normally distributed process, about 99.73% of all samples should fall within these limits if the process is in control.

Question 17

The general practice in quality control is to set the control chart's upper and lower control limit values equal to the variable's mean value +/-
A)1 standard deviation
B)2 standard deviations
C)2.5 standard deviations
D)3 standard deviations

Accepted Answer

The answer of The general practice in quality control is...

Question 18

A graphical tool used to help determine whether a process is in control or out of control is a
A)scatter diagram
B)histogram
C)control chart
D)None of the other answers is correct.

Accepted Answer

A control chart is specifically designed to monitor a process over time and identify when it is in or out of control. It includes upper and lower control limits based on the process data, and any data points outside of these limits indicate a process that is out of control and requires further investigation. Scatter diagrams and histograms are not specifically designed for this purpose.

Question 19

Which of the following is a statistical method used in quality control?
A)statistical process control
B)acceptance sampling
C)Both statistical process control and acceptance sampling are correct.
D)None of the other answers is correct.

Accepted Answer

Both statistical process control and acceptance sampling are commonly used statistical methods in quality control. Statistical process control involves monitoring and controlling a process to ensure it is operating within predetermined limits, while acceptance sampling involves inspecting a random sample of products or services to determine if they meet predetermined quality standards. Therefore, both methods are correct answers to this question.

Question 20

If the calculated lower-control limit of a p chart is negative,
A)a mistake has been made in the calculations
B)use the absolute value of the lower limit
C)it is set to zero
D)None of the other answers is correct.

Accepted Answer

The answer of If the calculated lower-control limit of a...

Quiz 14: Statistical Methods for Quality Control

A control chart that is used when the output of a production process is measured in terms of the proportion defective is

Normal or natural variation in the quality of production output that is due purely to chance is called

The sample result plotted on an np control chart is

A control chart that is used to monitor the range of the measurements in a sample is

Quality assurance consists of

A control chart used when the output of a process is measured in terms of the mean value of a variable such as a length, weight, temperature, and so on is

Variation in the quality of production output that is due to factors such as machine tools wearing out is called

A control chart that is used to monitor the number of defectives in a sample is

If the value of c in a single-stage acceptance sampling plan is increased, with n remaining constant, the probability of accepting the lot

The entire system of policies, procedures, and guidelines established by an organization to achieve and maintain quality is called

An operating characteristic curve is based on a ________ probability distribution.

Control charts that are based on data indicating the presence of a defect or the number of defects are called ______ control charts.

Which of the following is not a type of a control chart?

__________ consist(s) of making a series of inspections and measurements to determine whether quality standards are being met.

The control limits for a p chart are how many standard deviations above and below the proportion defective?

The control limits for an x-bar chart are how many standard deviations above and below the process mean?

The general practice in quality control is to set the control chart's upper and lower control limit values equal to the variable's mean value +/-

A graphical tool used to help determine whether a process is in control or out of control is a

Which of the following is a statistical method used in quality control?

If the calculated lower-control limit of a p chart is negative,