Deck 3: Statistical Process Control

Question 1

The average outgoing quality (AOQ) is a measure of the expected number of defective items that will pass on to the customer with the sampling plan selected.

Answer 1

True

Question 2

The simplest form of a sampling plan is a single-sample attribute plan.

Answer 2

True

Question 3

Choosing among a single-, double- and multiple-sampling plans is a strategic versus an economic decision.

Answer 3

False

Question 4

The probability of rejecting a lot that has an acceptable quality level is referred to as the

A) producer's risk.
B) consumer's risk.
C) lot tolerance percent defective.
D) acceptable quality level.

Question 5

With a single-sample attribute plan, only one of the items randomly sampled from a lot is inspected.

Question 6

A sampling plan provides a set of guidelines for accepting a lot.

Question 7

Six Sigma companies report

A) defective parts per million.
B) defective parts per thousand.
C) defective parts per hundred.
D) no defective parts.

Question 8

A multiple-sampling plan uses the smallest sample size of any sampling plan.

Question 9

Acceptance sampling is based on the premise that a lot contains some acceptable number of defective items.

Question 10

With acceptance sampling, a lot is either rejected or accepted depending on the number of defects found in a sample.

Question 11

Double-sampling plans are often less costly than single-sampling plans.

Question 12

Acceptance sampling involves the inspection of a non-random sample of units selected from a lot.

Question 13

A lot is rejected if the number of defective units found in a random sample exceeds a predetermined acceptable number of defective units.

Question 14

Acceptance sampling is consistent with TQM's philosophy of zero defects.

Question 15

The probability of accepting a lot that has a higher percentage of defective items than the lot tolerance percent defective is referred to as the

A) producer's risk.
B) sampling plan.
C) consumer's risk.
D) average outgoing quality.

Question 16

The consumer's risk is the probability of rejecting a lot that meets the acceptable quality level (AQL).

Question 17

Acceptance sampling is still used today for all the following reasons except

A) government regulations.
B) contractual requirements.
C) industry standards.
D) total quality management principles.

Question 18

An operating characteristics (OC) curve is a graph that measures the probability of accepting a lot with no defective items.

Question 19

The consumer's risk is the probability of accepting a lot in which the fraction of defective items exceeds the lot tolerance percent defective (LTPD).

Question 20

Six Sigma companies report defective parts per million (PPM) versus the more traditional defective parts per hundred.

Question 21

A(n) ___ curve is a graph showing the probability of accepting a lot for different quality levels with a specific sampling plan.

A) operating characteristic (OC)
B) average outgoing quality
C) lot tolerance percent defective
D) single-sample attribute

Question 22

Unique or special cause variation reflects the random variation associated with the output of a process.

Question 23

Discuss the rationale and procedure for the initial construction of a control chart.

Question 24

Statistical process control involves monitoring and controlling a process to prevent poor quality.

Question 25

Is acceptance sampling consistent with TQM?

Question 26

Which sampling plans are typically the least expensive?

A) single-sampling plans.
B) double -sampling plans.
C) multiple-sampling plans.
D) cannot be determined without further information.

Question 27

Describe a double-sampling plan and explain its objective.

Question 28

Evaluate the process capability of a process.

Question 29

The ___ is the maximum number of defective items a customer will accept in a lot.

A) producer's risk
B) consumer's risk
C) average outgoing quality
D) lot tolerance percent defective

Question 30

Use variable control charts Variable control charts are used for continuous variables that can be measured, such as weight or volume.

Question 31

Typically, the operating characteristic curve shows the following on the horizontal and vertical axis (answers are given as horizontal axis and vertical axis respectively):

A) proportion defective and probability of acceptance.
B) proportion non-defective and probability of acceptance.
C) proportion defective and probability of rejection.
D) proportion non-defective and probability of rejection.

Question 32

Use attribute control charts. The quality measures used in attribute control charts are discrete values reflecting a simple decision criterion such as good or bad.

Question 33

The expected number of defective items that will pass on to the customer with a sampling plan is known as the

A) lot tolerance percent defective.
B) acceptable quality level.
C) average outgoing quality.
D) sampling plan.

Question 34

An operating characteristic (OC) curve is a graph that measures

A) the acceptable proportion of defects in a lot to the consumer.
B) the probability of accepting a lot for different quality levels with a specific sampling plan.
C) the probability of accepting a lot in which the fraction of defectives exceeds the lot tolerance percent defective.
D) the maximum number of defective items a consumer will accept in a lot.

Question 35

What is the advantage of a multiple-sampling plan?

Question 36

Explain the basics of applying statistical process control (SPC) in production and services.

Question 37

Identify control chart patterns and describe appropriate data collection.

Question 38

The acceptable quality level is

A) the maximum number of defective items a consumer will accept in a lot.
B) an acceptable proportion of defective items in a lot to the consumer.
C) the minimum number of defective items a consumer will accept in a lot.
D) none of the above.

Question 39

The consumer's willingness to accept lots with a small proportion of defective items is known as the acceptable

A) sampling plan.
B) quality level.
C) consumer's risk.
D) producer's risk.

Question 40

The average outgoing quality is

A) the expected number of non-defective items that will pass on to the customer with a sampling plan.
B) the number of defective items in a lot that the customer is willing to accept.
C) the expected number of defective items that will pass on to the customer with a sampling plan.
D) the number of defective items in a lot that the customer is not willing to accept.

Question 41

Process control charts are rarely useful for monitoring and controlling the output of service processes.

Question 42

Statistical process control is a tool used to monitor and improve quality.

Question 43

The individual that detects special cause variation in a process is not allowed to diagnose the root cause and correct it.

Question 44

Common cause (random) variation provides evidence that the process is not in control.

Question 45

All processes contain a certain amount of variation in their output.

Question 46

One goal of statistical process control is to prevent a process from producing items that have to be scrapped or reworked.

Question 47

After special cause variation is detected, the focus changes to identifying the root cause of the variation and eliminating it.

Question 48

Statistical process control is based on a philosophy of inspection as opposed to prevention.

Question 49

One reason some companies fail in their attempt to apply statistical process control is lack of training.

Question 50

Process control charts are often used at a critical point after which it is difficult to correct or rework the process output.

Question 51

Employee training in statistical process control is a fundamental principle in total quality management programs.

Question 52

Control limits are based on the special cause variation inherent in a process.

Question 53

A process that is determined to be in control contains no variation.

Question 54

Special cause variation can be identified using statistical process control.

Question 55

Two types of variation associated with the output of a process are common (random) cause and special cause.

Question 56

Process control is achieved by taking periodic samples from a process and plotting the sample points on a chart to determine if the process is within control limits.

Question 57

A quantitative variable classifies while a qualitative variable (attribute) measures.

Question 58

Control charts visually show when a process is not within statistical control limits.

Question 59

Statistical process control is a subset of statistical quality control.

Question 60

Statistical process control is only effective for service processes.

Question 61

A c-chart monitors the number of defects in small samples.

Question 62

When special cause variation is detected, it is normally eliminated by increasing the number of standard deviations (z value) used to calculate the control limits.

Question 63

When monitoring a process's output with a quantitative variable either an R-chart or an -chart is used, but never both.

Question 64

A p-chart is used to monitor the proportion defective in the output of a process.

Question 65

Construction and use of an -chart is based on an assumption that the sample points are normally distributed around the centre line.

Question 66

When calculating control limits for a process, the number of standard deviations (z value) is typically six.

Question 67

The R-chart is used for monitoring and controlling variation within samples.

Question 68

Attribute (qualitative) control charts are used to monitor descriptive characteristics of the output of a process.

Question 69

The smaller the historical proportion defective reported for a process, the larger the sample size required to detect special cause variation with a p-chart.

Question 70

Control charts are never implemented until special cause variation has been detected in a process.

Question 71

The range is the difference between the smallest and largest values in a sample.

Question 72

With a c-chart, the sample size is small and often contains only one item.

Question 73

It is possible to have low variation within samples while at the same time having high variation between sample means.

Question 74

The range measures the variation within samples versus the variation between samples.

Question 75

The formula used to determine the upper and lower control limits is based on specification limits.

Question 76

It is sometimes not necessary to determine new control limits after special cause variation has been identified if the source has been eliminated without changing the process.

Question 77

Variable control charts are used for quantitative measures such as weight or time.

Question 78

Variable (quantitative) control charts are used to monitor measurable characteristics of a process's outputs.

Question 79

Defect and defective mean the same thing for attribute (qualitative) control charts.

Question 80

When a control chart detects no special cause variation in a process, the upper and lower control limits are the same value.