28. A control chart controls a manufacturing process. Measurements are
taken while the process is operating one time each hour. At each hour
five sample parts are measured, and the results are recorded and plotted
on a control chart. During the last five hours the following data was
observed for X bar and R. The upper control limit for X bar values is
142 and the lower control limit is 102. The value on the control chart
for X bar is 122 and the value for R bar is 3. What can be said about
this process?
9
A.M. 10
A.M. 11
A.M. 12
A.M. 1
P.M.X bar 125 126 127 128 129
R 2 1 4 2 3
a. The process is not in control and should be adjusted.
b. The process is in control and should not be adjusted.
c. The value of R is too high at 11 . .
d. The value for X bar is outside the control limits.
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