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CHAPTER 21 SECTION 3: STATISTICAL PROCESS CONTROL
MULTIPLE CHOICE
61.
The mean of the sample means and the pooled standard deviation of 25 samples of size 4 taken from a
production process under control are found to be 150 and 10, respectively. The centerline for the
x
chart
is:
a.
150
b.
100
c.
250
d.
6
ANS: A
PTS:
1
REF:
SECTION 21.3
62.
To determine whether the process distribution standard deviation has changed, we use a(n):
a.
x
chart.
b.
S
chart.
c.
p
chart.
d.
All of these choices are true.
ANS: B
PTS:
1
REF:
SECTION 21.3
63.
To determine whether the proportion of defectives is in line with specifications, we use a(n):
a.
x
chart.
b.
S
chart.
c.
p
chart.
d.
All of these choices are true.
ANS: C
PTS:
1
REF:
SECTION 21.3
64.
Control charts used to determine if the process distribution standard deviation has changed are:
a.
x
and
p
charts.
b.
p
and
R
charts.
c.
R
and
S
charts.
d.
S
and
x
charts.
ANS: C
PTS:
1
REF:
SECTION 21.3
65.
The mean of the sample means and the pooled standard deviation of 40 samples of size 5 taken from a
production process under control are found to be 400 and 15, respectively. The lower control limit for
the
x
chart is:
a.
460.37
b.
392.88
c.
379.88
d.
None of these choices.
ANS: C
PTS:
1
REF:
SECTION 21.3
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66.
If the upper and lower specification limits of a process are 0.852 and 0.828, respectively, and the
process standard deviation is 0.002, then the process capability index
C
p
is
a.
0.024
b.
2.000
c.

2.000
d.
12.000
ANS: B
PTS:
1
REF:
SECTION 21.3
67.
The mean of the sample means and the pooled standard deviation of 50 samples of size 10 taken from a
production process under control are found to be 225 and 16, respectively. The upper control limit for
the
x
chart is:
a.
231.79
b.
240.18
c.
218.21
d.
209.82
ANS: B
PTS:
1
REF:
SECTION 21.3
TRUE/FALSE
68.
When the purpose of sampling is to detect when a process becomes too variable, the control chart of
choice will be an
S
chart.
ANS: F
PTS:
1
REF:
SECTION 21.3
69.
For an
x
chart, the lower and upper control limits are usually set at three standard errors from the
centerline.
ANS: T
PTS:
1
REF:
SECTION 21.3
70.
A process capability index (
C
p
) of 2.0 describes a production process where the specification limits are
equal to 3 standard errors above and below the centerline.
ANS: F
PTS:
1
REF:
SECTION 21.3
71.
The process capability index measures the capability of the process to produce units whose dimensions
fall with in the specifications.
ANS: T
PTS:
1
REF:
SECTION 21.3
72.
A coffee machine fills cups with an average of 6 ounces with a standard deviation of 0.25 ounces. A
sample of 9 cups is taken. The lower and upper control limits for a 3sigma
x
control chart are 5.75 and
6.25, respectively.
ANS: T
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This note was uploaded on 09/28/2010 for the course FINOPMGT 250 taught by Professor Kumar during the Spring '10 term at University of Massachusetts Boston.
 Spring '10
 Kumar

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