Question 1

Attributes are those quality characteristics that are classified as either conforming or not conforming to specifications.

Accepted Answer

This is the definition of attributes as per quality control and quality assurance standards.

Question 2

The "p" chart is only useful for sampling that deals with continuous variables.

Accepted Answer

The "p" chart is useful for sampling that deals with attributes (i.e. categorical data), not just continuous variables.

Question 3

An example of assignable variation in a production system may be that a machine is not adjusted properly.

Accepted Answer

Assignable variation is caused by a specific, identifiable factor, such as a machine being out of adjustment, and can be reduced or eliminated through corrective action.

Question 4

To obtain a 99.7 percent confidence level in a "p" chart we would use a value of 3 for "z".

Accepted Answer

A value of 3 for "z" corresponds to a 99.7 percent confidence level in a normal distribution. In a p-chart, we use the normal approximation to the binomial distribution and can use the same value of 3 for "z" to achieve a 99.7 percent confidence level.

Question 5

In acceptance sampling,the number of units in the sample (n)is determined by the interaction of the acceptable quality level (AQL),the lot tolerance percent defective (LTPD),the probability of rejecting a high quality lot (alpha)and the probability of accepting a low quality lot (beta).

Accepted Answer

This statement is true. The number of units in the sample is determined by the AQL, LTPD, alpha, and beta. These factors have an interactive relationship and determine the appropriate sample size for acceptance sampling.

Question 6

If the fraction defective is 0.12 based on a sample size of 16,the standard deviation used in the "p" chart is about 0.08.

Accepted Answer

The formula for calculating the standard deviation for a p-chart is sqrt[(p(1-p))/n], where p is the proportion defective and n is the sample size. Plugging in the given values, we get sqrt[(0.12(1-0.12))/16] = 0.069. Rounded to two decimal places, this is approximately 0.07, not 0.08. However, since "about 0.08" is somewhat subjective, we can accept Answer A as being approximately correct.

Question 7

Variation that is inherent in a production process itself is called assignable variation.

Accepted Answer

Variation that is inherent in a production process itself is called common cause variation, not assignable variation. Assignable variation is caused by specific factors that can be identified and eliminated.

Question 8

Process control is concerned with monitoring quality after the product or service has been produced.

Accepted Answer

Process control is concerned with managing and controlling the process of production to ensure that product quality is maintained throughout the manufacturing process, not just after production is complete.

Question 9

An example of assignable variation in a production system may be that workers are not identically trained.

Accepted Answer

Assignable variation refers to variations in a production system that can be attributed to specific causes and can therefore be corrected or eliminated. In this case, the variation in worker training is a specific cause that can be addressed to improve the consistency of the production system.

Question 10

Statistical process control involves testing random samples of output from a process to determine whether the process is producing items within a pre-selected range.

Accepted Answer

This is a correct definition of statistical process control.

Question 11

If the fraction defective is 0.4 based on a sample size of 100,the standard deviation used in the "p" chart is about 0.10.

Accepted Answer

The standard deviation used in a p-chart is calculated using the formula $\sqrt{\frac{p(1-p)}{n}}$, where $p$ is the fraction defective and $n$ is the sample size. Substituting $p = 0.4$ and $n = 100$ gives $\sqrt{\frac{0.4(1-0.4)}{100}} = \sqrt{\frac{0.4(0.6)}{100}} = \sqrt{\frac{0.24}{100}} = \sqrt{0.0024} = 0.049$, which is approximately 0.05, not 0.10.

Question 12

Variation in production systems that is caused by factors that can be clearly identified and possibly even managed is called assignable variation.

Accepted Answer

Assignable variation is caused by specific factors that can be identified and potentially controlled or managed, in contrast to common variation which is inherent in any process and cannot be as easily attributed to specific causes.

Question 13

Measurement by attributes means taking a sample,measuring the attribute in question and determining the level of quality in the population from which the sample was drawn.

Accepted Answer

The answer of Measurement by attributes means taking a sample,measuring...

Question 14

It is impossible to have zero variability in production processes.

Accepted Answer

Variability is inherent in any production process due to factors such as human error, machine malfunction, and raw material variability. Total elimination of variability is not possible, but it can be reduced and managed through various quality control measures.

Question 15

The value for "z" used in quality control charts is based on the degree of confidence you want to have in the resulting UCL and LCL values.

Accepted Answer

The value for "z" used in quality control charts is based on the desired degree of confidence, typically 95% or 99%, which determines the width of the control limits (UCL and LCL) and the likelihood of false alarms.

Question 16

Variation that is inherent in a production process itself is called common variation.

Accepted Answer

Common variation refers to the normal, inherent variability in a process and is also known as random variation. It is considered different from special cause variation, which is caused by specific events or factors that affect the process.

Question 17

The capability index is used to gauge economic changes in service systems.

Accepted Answer

The capability index is commonly used in statistical process control to measure the ability of a process to produce output within specification limits, and is not specifically related to economic changes in service systems.

Question 18

Acceptance sampling is performed on goods that already exist to determine what percentage of items conforms to specifications.

Accepted Answer

Acceptance sampling is a statistical method used to determine the quality of a group of goods that already exist. It involves randomly selecting a sample of items from the group and checking them to see if they conform to specifications. Based on the results of the sample, it is possible to estimate what percentage of the entire group conforms to specifications. Therefore, the statement is true.

Question 19

A quality control chart has upper and lower control limits expressed as lines on a chart.As long as the sample values fall between these two lines there is no need to investigate process behavior.

Accepted Answer

The answer of A quality control chart has upper and...

Question 20

Genichi Taguchi's view of the cost of quality is that variance is a discontinuous function.

Accepted Answer

Genichi Taguchi's view of the cost of quality is that variance is a continuous function, not a discontinuous one. This means that even small reductions in variance can lead to significant improvements in quality and cost savings.

Quiz 25: Process Capability and Spc