Question

Hello,

I need help with the following question. I think that the answer is “Individual outliers” since the central line for X bar is 58, LCL is 56.15 and UCL is 59.85. The range is 6.0. In my graph the majority of the points are outside the control limits. Please help me with this question. Thank you!

TABLE

Day	Sample mean (in minutes)	R (Range)
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	60.9	6.5
13	58.3	5.9
14	52.0	5.2

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.

Referring to Table 17-3, suppose the analyst constructs an X double bar chart to see if the production process is in-control. Which expression best describes this chart?

		In-control
		Increasing trend
		Decreasing trend
		Individual outliers

Answer 1

The answer is:

Individual outliers

Explanation:

There are assignable causes of variation.

The process is out-of-control.

There are individual outliers.