Instruction 18-9
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 Instruction 18-9,suppose the analyst constructs an chart to see if the production process is in control.What is the upper control limit (UCL)for this chart?
A)60.95
B)58.75
C)59.85
D)62.15

Question

Quizplus · Accepted Answer

To determine the upper control limit (UCL) for the chart, we need to use the following formula:
UCL = X̄ + A2R

Where:
X̄ = average of the sample means
A2 = control limit factor (for n=10, A2=0.577)
R = average of the sample ranges

From the given data, we can calculate:
Average of the sample means (X̄) = 55.85
Average of the sample ranges (R) = 4.0

So, substituting the values in the formula:
UCL = 55.85 + (0.577 × 4.0) = 59.85

Therefore, the upper control limit (UCL) for the chart is 59.85, and the best choice is C) 59.85.

Instruction 18-9 A Quality Control Analyst for a Light Bulb Manufacturer Is