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 R chart to see if the variability in production times is in control.What is the lower control limit for this R chart?
A)4.84
B)2.98
C)1.34
D)3.37

Question

Quizplus · Accepted Answer

The lower control limit (LCL) for an R chart is calculated using the formula LCL = D3 * R-bar, where D3 is a constant that depends on the sample size (n=10 in this case) and R-bar is the average range. For n=10, D3 is typically 0, making the LCL = 0. However, if a specific R-bar is given or calculated, the LCL would be D3 * R-bar. Without specific R-bar, the closest choice is 1.34, assuming a non-zero D3 was used.

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