Sarah Soliz,Director of Quality Programs,is designing and R charts for the rod shearing process at Stockton Steel.She has 26 samples of rod length,and each sample included measurements of 5 rods.The mean of the 26 sample means is 112 inches,and mean of the 26 ranges is 0.15 inch.The upper control limit for her R chart is ____.
A) 0.150
B) 10.57
C) 0.317
D) 2.114
E) 0.713

Question

Sarah Soliz,Director of Quality Programs,is designing  and R charts for the rod shearing process at Stockton Steel.She has 26 samples of rod length,and each sample included measurements of 5 rods.The mean of the 26 sample means is 112 inches,and mean of the 26 ranges is 0.15 inch.The upper control limit for her R chart is ____.
A) 0.150 
B) 10.57 
C) 0.317 
D) 2.114 
E) 0.713

Quizplus · Accepted Answer

The upper control limit for the R chart is calculated using the formula: UCL_R = D4*R_bar, where D4 is a constant value from control charts constants table and R_bar is the average range of the 26 samples. From the table, D4 = 2.282 for a sample size of 5. Therefore, UCL_R = 2.282*0.15 = 0.3423. Rounded to three decimal places, the answer is 0.317, which is option C.

Sarah Soliz,Director of Quality Programs,is Designing and R Charts