SCENARIO 19-3 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.
-Referring to Scenario 19-3, suppose the analyst constructs an chart to see if the production process is in-control.What is the center line for this chart?
A)64.3
B)59.5
C)58.0
D)57.1

Question

SCENARIO 19-3 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. 
-Referring to Scenario 19-3, suppose the analyst constructs an  chart to see if the production process is in-control.What is the center line for this chart?
A)64.3 
B)59.5 
C)58.0 
D)57.1

Quizplus · Accepted Answer

The center line for an X-Bar chart is the average of the sample means. Therefore, we need to calculate the overall average of the sample means. Adding up all the sample means and dividing by the number of samples gives us:

(63.5 + 59.7 + 61.5 + 61.3 + 56.5 + 58.9 + 58.8 + 55.6 + 57.5 + 59.8 + 61.5 + 60.9 + 61.2 + 57.4) / 14 = 59.0

Therefore, the center line for the X-Bar chart is 59.0.

SCENARIO 19-3 a Quality Control Analyst for a Light Bulb