ISDS 3115 Test 2 – Complete Study Guide &
Practice Questions And Answers Verified 100%
Correct
A process that is assumed to be in control with limits of 89 ± 2 had sample
averages for the x-bar chart of the following: 87.1, 87, 87.2, 89, 90, 88.5, 89.5, and
88. Is the process in control?
A) Yes.
B) No, one or more averages exceeded the limits.
C) Not enough information to tell.
D) No, there is a distinguishable trend.
E) No, two or more consecutive points are very near the lower (or upper) limit. -
ANSWER -e
Ten samples of a process measuring the number of returns per 100 receipts were
taken for a local retail store. The number of returns were 10, 9, 11, 7, 3, 12, 8, 4, 6,
and 11. Find the standard deviation of the sampling distribution for the p-bar chart.
A) There is not enough information to ANSWER the question.
B) .081
C) 8.1
D) .0273
E) .0863 - ANSWER -d
An x-bar control chart was examined and no data points fell outside of the limits.
Can this process be considered in control?
A) Not yet, there could be a pattern to the points.
B) Not yet, the R-chart must be checked.
C) Not yet, the number of samples must be known.
D) Yes.
E) Both A and B - ANSWER -e
Statistical process control charts:
A) display the measurements on every item being produced.
,B) display upper and lower limits for process variables or attributes and signal
when a process is no longer in control.
C) indicate to the process operator the average outgoing quality of each lot.
D) indicate to the operator the true quality of material leaving the process.
E) are a graphic way of classifying problems by their level of importance, often
referred to as the 80-20 rule. - ANSWER -b
The Central Limit Theorem:
A) is the theoretical foundation of the c-chart.
B) states that the average of assignable variations is zero.
C) allows managers to use the normal distribution as the basis for building some
control charts.
D) states that the average range can be used as a proxy for the standard deviation.
E) controls the steepness of an operating characteristic curve. - ANSWER -c
For a 3-sigma x-bar chart where the process standard deviation is known, the
upper control limit:
A) is 3σ below the mean of sample means for a 3σ control chart.
B) is 3σ above the mean of sample means for a 3σ control chart.
C) is 3σ/ below the mean of sample means for a 3σ control chart.
D) is 3σ/ above the mean of sample means for a 3σ control chart.
E) cannot be calculated unless the average range is known. - ANSWER -d
*Up to three standard deviations above or below the centerline is the amount of
variation that statistical process control allows for:*
A) Type I errors.
B) about 95.5% variation.
C) natural variation.
D) all types of variation.
E) assignable variation. - ANSWER -*******c
A manager wants to build 3-sigma x-bar control limits for a process. The target
value for the mean of the process is 10 units, and the standard deviation of the
process is 6. If samples of size 9 are to be taken, what will be the upper and lower
control limits, respectively?
,A) -8 and 28
B) 16 and 4
C) 12 and 8
D) 4 and 16
E) 8 and 12 - ANSWER -b
*Jars of pickles are sampled and weighed. Sample measures are plotted on control
charts. The ideal weight should be precisely 11 oz. Which type of chart(s) would
you recommend?*
A) p-chart
B) c-chart
C) both an x-bar chart and an R-chart
D) an x-bar chart, but not an R-chart
E) both a p-chart and a c-chart - ANSWER -c
If x-bar = 23 ounces, σ = 0.4 ounces, and n = 16, what will be the ±3σ control
limits for the x-bar chart?
A) 21.8 to 24.2 ounces
B) 23 ounces
C) 22.70 to 23.30 ounces
D) 22.25 to 23.75 ounces
E) 22.90 to 23.10 ounces - ANSWER -c
The usual purpose of an R-chart is to signal whether there has been a:
A) gain or loss in dispersion.
B) change in the percent defective in a sample.
C) change in the central tendency of the process output.
D) change in the number of defects in a sample.
E) change in the consumer's risk. - ANSWER -a
A manager wishes to build a 3-sigma range chart for a process. The sample size is
five, the mean of sample means is 16.01, and the average range is 5.3. From Table
S6.1, the appropriate value of D3 is 0, and D4 is 2.115. What are the UCL and
LCL, respectively, for this range chart?
A) 33.9 and 11.2
, B) 33.9 and 0
C) 11.2 and 0
D) 6.3 and 0
E) 31.91 and 0.11 - ANSWER -c
*Plots of sample ranges indicate that the most recent value is below the lower
control limit. What course of action would you recommend?*
A) Since there is no obvious pattern in the measurements, variability is in control.
B) One value outside the control limits is insufficient to warrant any action.
C) Lower than expected dispersion is a desirable condition; there is no reason to
investigate.
D) The process is out of control; reject the last units produced.
E) Variation is not in control; investigate what created this condition. - ANSWER -
e
To set x-bar chart upper and lower control limits, one must know the process
central line, which is the:
A) average of the sample means.
B) total number of defects in the population.
C) percent defects in the population.
D) size of the population.
E) average range. - ANSWER -a
According to the text, what is the most common choice of limits for control
charts?
A) ±1 standard deviation
B) ±2 standard deviations
C) ±3 standard deviations
D) ±3 standard deviations for means and ± 2 standard deviations for ranges
E) ±6 standard deviations - ANSWER -c
Which of the following is true of a p-chart?
A) The lower control limit is found by subtracting a fraction from the average
number of defects.
B) The lower control limit indicates the minimum acceptable number of defects.
Practice Questions And Answers Verified 100%
Correct
A process that is assumed to be in control with limits of 89 ± 2 had sample
averages for the x-bar chart of the following: 87.1, 87, 87.2, 89, 90, 88.5, 89.5, and
88. Is the process in control?
A) Yes.
B) No, one or more averages exceeded the limits.
C) Not enough information to tell.
D) No, there is a distinguishable trend.
E) No, two or more consecutive points are very near the lower (or upper) limit. -
ANSWER -e
Ten samples of a process measuring the number of returns per 100 receipts were
taken for a local retail store. The number of returns were 10, 9, 11, 7, 3, 12, 8, 4, 6,
and 11. Find the standard deviation of the sampling distribution for the p-bar chart.
A) There is not enough information to ANSWER the question.
B) .081
C) 8.1
D) .0273
E) .0863 - ANSWER -d
An x-bar control chart was examined and no data points fell outside of the limits.
Can this process be considered in control?
A) Not yet, there could be a pattern to the points.
B) Not yet, the R-chart must be checked.
C) Not yet, the number of samples must be known.
D) Yes.
E) Both A and B - ANSWER -e
Statistical process control charts:
A) display the measurements on every item being produced.
,B) display upper and lower limits for process variables or attributes and signal
when a process is no longer in control.
C) indicate to the process operator the average outgoing quality of each lot.
D) indicate to the operator the true quality of material leaving the process.
E) are a graphic way of classifying problems by their level of importance, often
referred to as the 80-20 rule. - ANSWER -b
The Central Limit Theorem:
A) is the theoretical foundation of the c-chart.
B) states that the average of assignable variations is zero.
C) allows managers to use the normal distribution as the basis for building some
control charts.
D) states that the average range can be used as a proxy for the standard deviation.
E) controls the steepness of an operating characteristic curve. - ANSWER -c
For a 3-sigma x-bar chart where the process standard deviation is known, the
upper control limit:
A) is 3σ below the mean of sample means for a 3σ control chart.
B) is 3σ above the mean of sample means for a 3σ control chart.
C) is 3σ/ below the mean of sample means for a 3σ control chart.
D) is 3σ/ above the mean of sample means for a 3σ control chart.
E) cannot be calculated unless the average range is known. - ANSWER -d
*Up to three standard deviations above or below the centerline is the amount of
variation that statistical process control allows for:*
A) Type I errors.
B) about 95.5% variation.
C) natural variation.
D) all types of variation.
E) assignable variation. - ANSWER -*******c
A manager wants to build 3-sigma x-bar control limits for a process. The target
value for the mean of the process is 10 units, and the standard deviation of the
process is 6. If samples of size 9 are to be taken, what will be the upper and lower
control limits, respectively?
,A) -8 and 28
B) 16 and 4
C) 12 and 8
D) 4 and 16
E) 8 and 12 - ANSWER -b
*Jars of pickles are sampled and weighed. Sample measures are plotted on control
charts. The ideal weight should be precisely 11 oz. Which type of chart(s) would
you recommend?*
A) p-chart
B) c-chart
C) both an x-bar chart and an R-chart
D) an x-bar chart, but not an R-chart
E) both a p-chart and a c-chart - ANSWER -c
If x-bar = 23 ounces, σ = 0.4 ounces, and n = 16, what will be the ±3σ control
limits for the x-bar chart?
A) 21.8 to 24.2 ounces
B) 23 ounces
C) 22.70 to 23.30 ounces
D) 22.25 to 23.75 ounces
E) 22.90 to 23.10 ounces - ANSWER -c
The usual purpose of an R-chart is to signal whether there has been a:
A) gain or loss in dispersion.
B) change in the percent defective in a sample.
C) change in the central tendency of the process output.
D) change in the number of defects in a sample.
E) change in the consumer's risk. - ANSWER -a
A manager wishes to build a 3-sigma range chart for a process. The sample size is
five, the mean of sample means is 16.01, and the average range is 5.3. From Table
S6.1, the appropriate value of D3 is 0, and D4 is 2.115. What are the UCL and
LCL, respectively, for this range chart?
A) 33.9 and 11.2
, B) 33.9 and 0
C) 11.2 and 0
D) 6.3 and 0
E) 31.91 and 0.11 - ANSWER -c
*Plots of sample ranges indicate that the most recent value is below the lower
control limit. What course of action would you recommend?*
A) Since there is no obvious pattern in the measurements, variability is in control.
B) One value outside the control limits is insufficient to warrant any action.
C) Lower than expected dispersion is a desirable condition; there is no reason to
investigate.
D) The process is out of control; reject the last units produced.
E) Variation is not in control; investigate what created this condition. - ANSWER -
e
To set x-bar chart upper and lower control limits, one must know the process
central line, which is the:
A) average of the sample means.
B) total number of defects in the population.
C) percent defects in the population.
D) size of the population.
E) average range. - ANSWER -a
According to the text, what is the most common choice of limits for control
charts?
A) ±1 standard deviation
B) ±2 standard deviations
C) ±3 standard deviations
D) ±3 standard deviations for means and ± 2 standard deviations for ranges
E) ±6 standard deviations - ANSWER -c
Which of the following is true of a p-chart?
A) The lower control limit is found by subtracting a fraction from the average
number of defects.
B) The lower control limit indicates the minimum acceptable number of defects.
