Deck 21: Statistical Methods for Quality Control

Question 1

Consumer's risk is

A) the same concept as the Producer's risk.
B) the probability of Type II error.
C) the probability of Type I error.
D) the probability of rejecting a good-quality lot.

Answer 1

the probability of Type II error.

Question 2

Variations in process output that are due to factors in the production process such as machine tools wearing out are _____ causes.

A) assignable
B) common
C) controllable
D) random

Answer 2

assignable

Question 3

Producer's risk is

A) the same as the Consumer's risk.
B) the probability of Type II error.
C) the probability of Type I error.
D) the probability of accepting a poor-quality lot.

Answer 3

the probability of Type I error.

Question 4

In practice, it is common to use the sample ________ to estimate the process _________. ​

A) ​variances, range
B) ​means, variance
C) ​standard deviations, mean
D) ​ranges, standard deviation

Question 5

In acceptance sampling, the risk of rejecting a good-quality lot is known as

A) Consumer's risk.
B) Producer's risk.
C) a Type II error.
D) None of these alternatives is correct.

Question 6

The maximum number of defective items that can be found in the sample and still lead to acceptance of the lot is

A) the upper-control limit.
B) the lower-control limit.
C) the acceptance criterion.
D) rejection criterion.

Question 7

A control chart that is used when the output of a production process is measured in terms of the percent defective is a(n) _____ chart.

A) P
B) X bar
C) process
D) np

Question 8

We can examine the effect of the sampling plan on both types of risks by varying the assumed​

A) ​percentage of defective items in the lot.
B) ​number of defective items in the sample.
C) ​probability of accepting the lot.
D) ​number of units in the lot.

Question 9

Setting the upper and lower control limits in a control chart farther from the center line results in a​

A) ​lower probability of a Type I error.
B) ​lower probability of a Type II error.
C) ​lower probability of both a Type I and Type II error.
D) ​higher probability of both a Type I and Type II error.

Question 10

Control charts based on data that can be measured on a continuous scale are called _____ control charts.

A) normal
B) variables
C) attributes
D) precision

Question 11

If the lower control limit of a P chart is negative,

A) a mistake has been made in the computations.
B) use the absolute value of the lower limit.
C) it is set to zero.
D) it is an indication that the process is out of control.

Question 12

Heavy emphasis on statistical analysis and careful measurement are closely associated with​

A) ​Total Quality Management.
B) ​ISO 9000.
C) ​Baldrige National Quality Program.
D) ​Six Sigma.

Question 13

Normal or natural randomly occurring variations in the quality of the production outputs that are due purely to chance are _____ causes.

A) assignable
B) common
C) controllable
D) random

Question 14

The process mean and standard deviation can be estimated by using samples that are selected from the process when​

A) ​it has only assignable-cause variation.
B) ​its output is uniformly distributed.
C) ​it is assumed to be operating in control.
D) ​it is operating at peak capacity.

Question 15

Setting the upper and lower control limits in a control chart closer to the center line results in a​

A) ​lower probability of a Type I error.
B) ​lower probability of a Type II error.
C) ​lower probability of both a Type I and Type II error.
D) ​higher probability of both a Type I and Type II error.

Question 16

A graph showing the probability of accepting the lot as a function of the percent defective in the lot is

A) a power curve.
B) a control chart.
C) an operating characteristic curve.
D) np ​curve.

Question 17

In acceptance sampling, the risk of accepting a poor-quality lot is known as

A) Consumer's risk.
B) Producer's risk.
C) a Type I error.
D) None of these alternatives is correct.

Question 18

Process control and acceptance sampling procedures are most closely related to _____ procedures.

A) linear regression
B) interval estimation
C) hypothesis testing
D) analysis of variance

Question 19

In quality control terminology, a group of items is a

A) sample.
B) bundle.
C) lot
D) stock.

Question 20

One purpose of control charts is to bring attention to the possible existence of _____ cause variation.

A) common
B) assignable .
C) both common and assignable
D) neither common or assignable

Question 21

Six Sigma represents a quality level of at most ____ defects per million opportunities.​

A) ​3.4
B) ​6.0
C) ​19.7
D) ​99.5

Question 22

Whenever assignable causes are detected, we conclude that the process is

A) out of control.
B) in statistical control.
C) controllable.
D) random.

Question 23

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

A) ​normal
B) ​exponential
C) ​binomial
D) ​uniform

Question 24

DFSS stands for​

A) ​Defects Found Sifting and Sorting
B) ​Design For Six Sigma
C) ​Deviation From Specifications and Standards
D) ​Defer For Statistical Study

Question 25

Control charts assist in detecting which type of process?

A) Out of control
B) In statistical control
C) Skewed control
D) None of these alternatives is correct.

Question 26

The second stage of a two-stage acceptance sampling plan is executed when the first-stage result is​

A) ​x₁ > c₁
B) ​c₁ < x₁ < c₂
C) ​x₁ > c₂
D) ​x₁ > c₁ + c₂

Question 27

The two general classifications of attributes in quality control are​

A) ​random and predictable.
B) ​controllable and uncontrollable.
C) ​variable and constant.
D) ​defective and nondefective.

Question 28

Control charts are classified by the

A) shape of the distribution.
B) type of data they contain.
C) null hypothesis.
D) sample size.

Question 29

When a Motorola executive said "That evaluation is …. perhaps the most cost-effective, value-added business consultation available anywhere in the world today" he was referring to​

A) ​ISO 9000 standards.
B) ​the Six Sigma philosophy.
C) ​Deming's 14 Points.
D) ​the Malcolm Baldrige Quality Award.

Question 30

A control chart that is used to monitor the variation of the measurements in a sample is a(n) _____ chart.

A) p
B) X
C) R
D) np

Question 31

The null hypothesis assumes that production process is

A) out of control.
B) in control.
C) changing.
D) random.

Question 32

A type II error would occur if we continued to allow the production process to be

A) out of control.
B) in statistical control.
C) adjusted when in control.
D) random.

Question 33

Juran proposed a simple definition of quality:​

A) ​customer satisfaction.
B) ​conformance to specifications.
C) ​fitness for use.
D) ​commitment to excellence.

Question 34

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

A) ​increases.
B) ​decreases.
C) remains unchanged.
D) ​might increase or decrease, depending on the lot percent defective.

Question 35

In contrast to Deming's philosophy, which required a major cultural change in the organization, Juran's programs were designed to improve quality by​

A) ​working within the current organizational system.
B) ​reducing the number of levels in the organizational structure.
C) ​changing customer perception and expectations.
D) ​identifying and replacing the most counter-productive employees.

Question 36

The three quality processes on which Juran's approach to quality focused include all of the following except quality

A) planning.
B) management.
C) control.
D) improvement.

Question 37

The Malcolm Baldrige National Quality Award was established in

A) ​1954.
B) ​1971.
C) ​1987.
D) ​1993.

Question 38

Adjustments or changes are necessary when the process is

A) out of control.
B) in statistical control.
C) in control.
D) working.

Question 39

The sample result plotted on an np control chart is​

A) ​the number of defects per part in the sample.​
B) ​the nominal percentage of correctable defects.
C) ​the number of perfect units in the sample.
D) ​the number of defective units in the sample.

Question 40

An chart is used if the quality of the output of the process is measured in terms of which level of measurement?

A) Nominal
B) Ordinal
C) Interval or ratio
D) Large sample

Question 41

An acceptance sampling plan uses a sample of 20 with an acceptance criterion of zero. Determine the probability of accepting shipments that contain 5, 10, 15, 20, 25, 30, 35, and 40% defective units.

Question 42

The quality control department of a company has decided to select a sample of 10 items from the shipments received; and if the sample contains no defective parts, the entire shipment will be accepted.
a.
If four percent of the items in the shipment are defective, what is the probability that the entire shipment will be accepted?
b.
Use the binomial table and read the probability of accepting shipments that contain 5, 10, 15, 20, 25, 30, 35, 40, 45, and 50% defective units.

Question 43

A production process that is in control has a mean (µ) of 189 and a standard deviation (σ) of 21.
Determine the lower and the upper control limits for sample sizes of 64.

Question 44

The results of inspection of samples of a product taken over the past 10 days are given below. Sample size for each day has been 140.
​ ​
Determine the 97% upper and lower control limits for the p-chart.

Question 45

The upper and lower control limits of the mean of a process are 700 and 650. Samples of size 169 are used for the inspection process. Determine the mean and the standard deviation for this process.

Question 46

In quality control terminology, the statistical procedure of acceptance sampling's alternative hypothesis is that

A) the lots are not equal.
B) lot 1 is greater than lot 2.
C) it is a good-quality lot.
D) it is a poor-quality lot.

Question 47

A production process is considered to be in control if it processes at least 97.5% nondefective items. Samples of size 450 are used for the inspection process. Determine the upper and lower control limits for the P chart of defective elements.

Question 48

A(n) _____ chart is used to monitor the proportion of defective in the sample.

A)
B) R.
C) p.
D) np.

Question 49

The results of inspection of samples of a product taken over the past 8 days are given below. Sample size for each day has been 120. Determine the 97% upper and lower control limits for the p-chart.

Question 50

In quality control acceptance sampling procedure, if the quality is not satisfactory, we would

A) reject the lot.
B) accept the lot.
C) try a different test.
D) send to customer.

Question 51

An chart could be used if the quality of the output of the process is measuring a process using sample

A) means.
B) variances.
C) ranges.
D) proportions.

Question 52

An estimator of the process standard deviation is the average _____ divided by a constant that depends on the sample size.

A) control
B) limit
C) constant
D) range

Question 53

The upper and lower control limits of the mean of a process are 66 and 54. Samples of size 25 are used for the inspection process. Determine the mean and the standard deviation for this process.

Question 54

A(n) _____ chart is used to monitor the range of measurements in the sample.

A)
B) R.
C) p.
D) np.

Question 55

A production process that is in control has a mean of 83 and a standard deviation of 17.
a.
Determine the upper and the lower control limits for a sample size of 30.
b.
Five samples had means of 80, 83, 74, 83, and 90. Indicate whether or not the process is in control.

Question 56

A(n) _____ chart is used to monitor the number of defectives in the sample.

A)
B) R.
C) p.
D) np.

Question 57

In quality control terminology, the statistical procedure of acceptance sampling's null hypothesis is that

A) the lots are not equal.
B) lot 1 is greater than lot 2.
C) it is a good-quality lot.
D) it is a poor-quality lot.

Question 58

The upper and lower control limits of the mean of a process are 672 and 654. Samples of size 256 are used for the inspection process. Determine the mean and the standard deviation for this process.

Question 59

In quality control terminology, the group of items being considered based on specified quality characteristics is called a

A) bin.
B) population.
C) lot.
D) sample.

Question 60

The upper and lower control limits of the mean of a process are 672 and 654. Samples of size 225 are used for the inspection process. Determine the mean and the standard deviation for this process.