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 centimetres, and mean of the 26 ranges is 0.15 centimetres.The upper control limit for her R chart is ___.

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 centimetres, and mean of the 26 ranges is 0.15 centimetres.The upper control limit for her R chart is ___.

Quizplus · Accepted Answer

Upper control limit for R chart = R-bar * D4
where R-bar = mean of ranges 
D4 = 2.115 (from the control chart constants for subgroup size = 5)
Upper control limit = 0.15 * 2.115 = 0.317
Therefore, the correct answer is C.

Sarah Soliz, Director of Quality Programs, Is Designing and R