TABLE 18-3
a Quality Control Analyst for a Light Bulb

TABLE 18-3
A quality control analyst for a light bulb manufacturer is concerned that the time it takes to produce a batch of light bulbs is too erratic. Accordingly, the analyst randomly surveys 10 production periods each day for 14 days and records the sample mean and range for each day.
$$\begin{array} { l c c } \text { Day } & \bar { X } ( \text { in minutes } ) & \text { R } \\\hline 1 & 58.5 & 5.1 \\2 & 47.6 & 7.8 \\3 & 64.3 & 6.1 \\4 & 60.6 & 5.7 \\5 & 63.7 & 6.2 \\6 & 57.5 & 6.0 \\7 & 55.0 & 5.4 \\8 & 54.9 & 6.1 \\9 & 55.0 & 5.9 \\10 & 62.7 & 5.0 \\11 & 61.9 & 7.1 \\12 & 60.0 & 6.5 \\13 & 58.3 & 5.9 \\14 & 52.0 & 5.2\end{array}$$
-Referring to Table 18-3, suppose the analyst constructs an $\bar{X}$ chart to see if the production process is in-control. What is the center line for this chart?

A) 64.3
B) 57.1
C) 58.0
D) 59.5