MGT 3200 Ch 10 - Quality Control

Two basic questions: concerning variability:

1, issue of process control 2. issue of process capability

4 managerial considerations in thinking about quality

1. At what points in the process to use control charts 2. What size samples to take 3. Sample frequency 4. What type of control chart to use

6 Steps required for effective control

1. Define 2. Measure 3. Compare 4. Evaluate 5. Correct 6. Monitor

4 inspection issues

1. How much to inspect and how often 2. At what points in the process to inspect 3. Whether to inspect in a centralized or on-site location 4. Whether to inspect attributes or variables

We are monitoring a process that has an outcome that is normally distributed with a mean of 100 and a standard deviation of 10. We would use _________ to evaluate whether this process's average is remaining in control. A) x-bar charts B) R-charts C) p-charts D) z-charts

A) x-bar charts

Suppose a process, when in control, has an average of 9 defects per unit. The lower and upper limits for the three-sigma control charts that would be used to monitor it would be, respectively, A) 3 and 12. B) 0 and 18. C) 6 and 24. D) 4.5 and 13.5.

B) 0 and 18.

Suppose that the grand process mean for a measured variable is 83. The upper control limit in the three-sigma control chart for this process's mean is 92. What would the lower control limit in the two-sigma control chart for this process's mean be? A) 79 B) 77 C) 71 D) 72

B) 77

We are monitoring a process that has an outcome that is normally distributed with a mean of 100 and a standard deviation of 10. We would use _________ to evaluate whether this process's variability is remaining in control. A) x-bar charts B) R-charts C) p-charts D) z-charts

B) R-charts

In statistical process control, attributes are characteristics that can be: A) measured. B) counted. C) observed. D) replicated.

B) counted

Which type of control chart would be appropriate if the variable being monitored is the number of students absent from section 1 of a statistics class? A) x-bar B) p C) R D) c

B) p

How many up/down runs are there in the following data: 5 2 3 5 4 3 2 1 2 4 A) 2 B) 3 C) 4 D) 5 E) 6

C) 4

If a process is not centered within its specification interval, use of the basic capability index, Cp, will lead to an assessment of capability that is: A) unbiased. B) too small. C) inflated. D) invariant.

C) inflated.

We are monitoring a process that has an outcome that falls into one of two categories. We would use __________ to evaluate whether this process is remaining in control. A) x-bar charts B) R-charts C) p-charts D) z-charts

C) p-charts

A point which is outside of the lower control limit on a c-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 control limit is always zero.

C) should be investigated because an assignable cause of variation might be present.

___________: How will measurement be accomplished?

Measure

___________: Verify that the problem has been eliminated

Monitor

_____________ control charts are Used to monitor the central tendency of a process

mean

Variables generate data that are _______________

measured

Inspection alone is generally not ____________ to achieve a reasonable level of ______________

sufficient, quality

________________ or _____________ Range of acceptable values established by engineering design or customer requirements

tolerances or specifications

Upper and lower control limits define the range of acceptable _____________

variation

______ bar chart are Used to monitor the central tendency of a process

x

__________: What is to be controlled?

Define

2 steps to maintaining quality standards

1. Product and service design 2, Increase capability in order to move from extensive use of control charts and inspection to achieve desired quality outcomes

5 typical inspection points

1. Raw materials and purchased parts 2. Finished products 3. Before a costly/bottleneck 4. operation 5. Before an irreversible process 6. Before a covering process

SPC involves periodically taking samples of process output and computing 2 sample statistics

1. Sample means 2. The number of occurrences of some outcome

5 steps of improving process capability

1. Simplify 2. Standardize 3. Mistake-proof 4. Upgrade equipment 5. Automate

3 phases of quality assurance from least to most progressive

1. acceptance sampling 2. process control 3. continuous improvement

4 steps of SPC

1. plan 2. do 3. study 4. act

2 types of control charts to use

1. variables 2. attributes

The ratio of a centered process's specification width to its process width is called the: A) capability index. B) control ratio. C) index chart. D) specification metric.

A) capability index.

____________: There must be a standard of comparison

Compare

____________: Uncover the cause of nonrandom variability and fix it

Correct

If a process that falls out of statistical control continues to produce a very large proportion of output that is acceptable, that process must be highly: A) in control. B) variable. C) attributable. D) capable.

D) capable.

The __________ the sample size, the __________ the sampling distribution. A) smaller; more accurate B) larger; more accurate C) smaller; less variable D) larger; less variable

D) larger; less variable

How many A/B median runs are there in the following data: 3 5 4 8 7 6 4 3 2 9 A) 2 B) 3 C) 4 D) 5 E) 6

E) 6

Narrowing control limits from 3s to 2s will increase the probability of making a(n) __________ error. A) Type I B) alpha C) Type III D) beta E) Type II

E) Type II

____________: Establish a definition of out of control

Evaluate

___________ ______________ ____________ Helps us to decide if a process is "in control" or if corrective action is needed

Statistical Process Control (SPC)

Most organization rely upon some ______________ and a great deal of _______________ _____________ to achieve an acceptable level of quality.

inspection, process control

Once a process has been determined to be stable, it is necessary to determine if the process is capable of producing output that is within an ______________ ___________________

acceptable range

______________ variation also known as special cause

assignable

______________ variation is Assignable (special cause) variation: A variation whose cause can be identified, and A nonrandom variation

assignable

Use a _____ chart Use only when the number of occurrences per unit of measure can be counted; non-occurrences cannot be counted

c

_____ chart are Control chart used to monitor the number of defects per unit

c

answers issue of process ____________: Given a stable process, is the inherent variability of the process within a range that conforms to performance criteria?

capability

qaulity of _______________ is A product or service conforms to specifications

conformance

answers issue of process ____________: Are the variations random? If nonrandom variation is present, the process is said to be unstable

control

__________ ____________ A time ordered plot of representative sample statistics obtained from an ongoing process (e.g. sample means), used to distinguish between random and nonrandom variability

control chart

___________ ___________ are The dividing lines between random and nonrandom deviations from the mean of the distribution

control limits

Sampling and corrective action are only a part of the ____________ ____________

control process

Attributes generate data that are _________________

counted.

Achieving and ____________ _______________ standards is of strategic importance to all business organizations

maintaining quality

________________ An appraisal activity that compares goods or services to a standard

inspection

Each point on the control chart represents a sample of ___ ____________________

n observations

Use a _____ chart When observations can be placed into two categories (good/bad, pass/fail, operate/dont)

p

Use a _____ chart When the data consists of multiple samples of several observations each

p

____ chart are Control chart used to monitor the proportion of defectives in a process

p

Quality is a _____________ ____________ for nearly all customers

primary consideration

___________ ____________ The inherent variability of process output (process width) relative to the variation allowed by the design specification (specification width)

process capability

______________ _____________ Natural or inherent variability in a process

process variability

Sample statistics are used to judge the randomness of ____________ ____________

process variation

______________ __________ A process that evaluates output relative to a standard and takes corrective action when output doesn't meet standards

quality control

____________ variation is Natural variation in the output of a process, created by countless minor factors

random

______________ variation is also known as common cause

random

___________ charts are Used to monitor process dispersion

range

______________ control charts are Used to monitor the process dispersion

range

_____________ ______________ _______________ (________) Statistical evaluation of the output of a process

statistical process control (SPC)