TABLE 18-4
A factory supervisor is concerned that the time it takes workers to complete an important production task (measured in seconds) is too erratic and adversely affects expected profits. The supervisor proceeds by randomly sampling 5 individuals per hour for a period of 10 hours. The sample mean and range for each hour are listed below.
$$\begin{array} { l l l l }
\text { Hour } & \bar { X } & \text { R } \
\hline 1 & 18.4 & 25 \
2 & 16.9 & 27 & \
3 & 23.0 & 30 & \
4 & 21.2 & 23 & \
5 & 21.0 & 24 & \
6 & 24.0 & 25 & \
7 & 19.3 & 12 \
8 & 15.8 & 14 & \
9 & 20.0 & 13 & \
10 & 23.0 & 11 &
\end{array}$$ She also decides that lower and upper specification limit for the critical-to-quality variable should be 10 and 30 seconds, respectively.
-Referring to Table 18-4, suppose the supervisor constructs an$\bar{ X}$ chart to see if the process is in-control. Which expression best describes this chart?
A) cycles
B) decreasing trend
C) hugging the center line
D) increasing trend

Question

TABLE 18-4
A factory supervisor is concerned that the time it takes workers to complete an important production task (measured in seconds) is too erratic and adversely affects expected profits. The supervisor proceeds by randomly sampling 5 individuals per hour for a period of 10 hours. The sample mean and range for each hour are listed below.
 $$\begin{array} { l l l l } 
\text { Hour } & \bar { X } & \text { R } \
\hline 1 & 18.4 & 25 \
2 & 16.9 & 27 & \
3 & 23.0 & 30 & \
4 & 21.2 & 23 & \
5 & 21.0 & 24 & \
6 & 24.0 & 25 & \
7 & 19.3 & 12 \
8 & 15.8 & 14 & \
9 & 20.0 & 13 & \
10 & 23.0 & 11 &
\end{array}$$ She also decides that lower and upper specification limit for the critical-to-quality variable should be 10 and 30 seconds, respectively.
-Referring to Table 18-4, suppose the supervisor constructs an$\bar{ X}$ chart to see if the process is in-control. Which expression best describes this chart?
A) cycles
B) decreasing trend
C) hugging the center line
D) increasing trend

Quizplus · Accepted Answer

The X chart is used to monitor the process mean. If the process is in control, the data points should hug the center line. Therefore, option C, hugging the center line, is the best description of the X chart. Options A and D refer to patterns that may indicate the process is out of control, while option B implies a consistent decrease in the values and not necessarily a measure of control.

TABLE 18-4 a Factory Supervisor Is Concerned That the Time

TABLE 18-4
a Factory Supervisor Is Concerned That the Time