Operations Management – Chapter 10 – Flashcards

Approving the effort that occurs during the production process is known as acceptance sampling.

Statistical Process Control is the measurement of rejects in the final product.

The optimum level of inspection occurs when we catch at least 98.6 percent of the defects.

The optimum level of inspection minimizes the sum of inspection costs and the cost of passing defectives.

Processes that are in control eliminate variations.

High-cost, low-volume items often require careful inspection since we make them so infrequently.

Low-cost, high-volume items often require more intensive inspection.

A lower control limit must by definition be a value less than an upper control limit.

Attributes need to be measured, variable data can be counted.

The amount of inspection we choose can range from no inspection at all to inspecting each item numerous times.

The amount of inspection needed is governed by the costs of inspection and the expected costs of passing defective items.

The purpose of statistical process control is to ensure that historical output is random.

A process that exhibits random variability would be judged to be out of control.

If a point on a control chart falls outside one of the control limits, this suggests that the process output is non-random and should be investigated.

An x-bar control chart can only be valid if the underlying population it measures is a normal distribution.

Concluding a process is out of control when it is not is known as a Type I error.

An R value of zero (on a range chart) means that the process must be in control since all sample values are equal.

Range charts are used mainly with attribute data.

Range charts and p-charts are both used for variable data.

A p-chart is used to monitor the fraction of defectives in the output of a process.

A c-chart is used to monitor the total number of defectives in the output of a process.

A c-chart is used to monitor the number of defects per unit for process output.

Tolerances represent the control limits we use on the charts.

"Process capability" compares "process variability" to the "tolerances."

Control limits used on process control charts are specifications established by design or customers.

Control limits tend to be wider for more variable processes.

Patterns of data on a control chart suggest that the process may have non-random variation.

The output of a process may not conform to specifications even though the process may be statistically "in control."

Run tests are useful in helping to identify nonrandom variations in a process.

Run tests give managers an alternative to control charts; they are quicker and cost less.

Statistical process control focuses on the acceptability of process output.

A run test checks a sequence of observations for randomness.

Even if the process is not centered, the process capability index (indicated by Cpk) is very useful.

The process capability index (indicated by Cpk) can be used only when the process is centered.

Quality control is assuring that processes are performing in an acceptable manner.

The primary purpose of statistical process control is to detect a defective product before it is shipped to a customer.

The Taguchi Cost Function suggests that the capability ratio can be improved by extending the spread between LCL and UCL.

The variation of a sampling distribution is tighter than the variation of the underlying process distribution.

The sampling distribution can be assumed to be approximately normal even when the underlying process distribution is not normally distributed.

Approximately 99.7% of sample means will fall within ± two standard deviations of the process mean if the process is under control.

The best way to assure quality is to use extensive inspection and control charts.

Control limits are based on multiples of the process standard deviation.

Attribute data are counted, variable data are measured.

The number of defective parts in a sample is an example of variable data because it will "vary" from one sample to another.

Larger samples will require wider x-bar control limits because there is more data.

When a process is not centered, its capability is measured in a slightly different way. The symbol for this case is Cpk.

Range control charts are used to monitor process central tendency.

An "up and down" run test uses the median as a reference point and measures the percentage above and below the median.

"Assignable variation" is variation due to a specific cause, such as tool wear.

Variation in a sample statistic collected from a process may be either random variation or assignable variation - or both.

"Quality of conformance" is concerned with whether a product or service conforms to its specifications.

The larger the process variation, the tighter the specifications should be.

Type I and Type II errors refer to the magnitude of variation from the standard.

The greater the capability ratio, the higher the rejects.

Non-random variation is likely whenever all observations are between the LCL and UCL.

The more effective and all-encompassing a firm's quality control and continuous improvement efforts, the less that company will need to rely on: A. insourcing. B. inspection. C. outsourcing. D. acceptance sampling. E. capability assessment.

Inspection is a(n): A. prevention. B. control. C. monitoring. D. corrective. E. appraisal.

Quality control, in contrast to quality assurance, is implemented: A. after production. B. before inspection. C. by self-directed teams. D. by top management. E. during production.

Which of the following quality control sample statistics indicates a quality characteristic that is an attribute? A. mean B. variance C. standard deviation D. range E. proportion

A time-ordered plot of representative sample statistics is called a: A. Gantt chart B. SIMO-chart C. Control Chart D. Up-Down Matrix E. Standard deviation table

A control chart used to monitor the process mean is the: A. p-chart B. R-chart C. x-bar chart D. c-chart E. Gantt chart

A control chart used to monitor the fraction of defectives generated by a process is the: A. p-chart B. R-chart C. x-bar chart D. c-chart E. Gantt chart

A p-chart would be used to monitor _______. A. average shrinkage B. dispersion in sample data C. the fraction defective D. the number of defects per unit E. the range of values

A c-chart is used for: A. means B. ranges C. percent defective D. fraction defective per unit E. number of defects per unit

A control chart used to monitor the number of defects per unit is the: A. p-chart B. R-chart C. x-bar chart D. c-chart E. Gantt chart

A point which is outside of the lower control limit on an R-chart: A. is an indication that no cause of variation is present B. should be ignored because it signifies better than average quality C. should be investigated because an assignable cause of variation might be present D. should be ignored unless another point is outside that limit E. is impossible since the lower limit is always zero

If a process is performing as it should, it is still possible to obtain observations which are outside of which limits? (I) tolerances (II) control limits (III) process variability A. I B. II C. I and II D. II and III E. I, II, and III

Which of the following relationships must always be incorrect? A. Tolerances > process variability > control limits B. Process variability > tolerances > control limits C. Tolerances > control limits > process variability D. Process variability > control limits > tolerances E. Process variability