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 5 production periods each day for 8 days and records the sample mean and range for each day.

Day X (in minutes) Range

1 13.6 3.5

2 14.3 4.1

3 15.3 5.0

4 12.6 2.8

5 11.8 3.7

6 12.9 4.8

7 17.3 4.5

8 15.8 2.4

Construct a X /R chart table and determine whether the X chart process is:

A) increasing trend B) decreasing trend C) at least one point is outside of the control limits. D) in-control.