A metals refining company recently implemented a new process for producing high-quality iron nuggets directly from raw iron ore and coal. To assess the capability and stability of the process, a quality engineer sampled and measured the percentage change in carbon content every 4 hours. The following table presents the % change in carbon content measurement the 33 samples. (a) Assess process control and stability. What is the standard deviation estimate of the in control, stable process? (b) Prepare a normal probability plot of the % change in carbon content measurements. At = 0.05, do the data fit a normal distribution? (c) If the % change in carbon content specification is 3.50 0.50, estimate the process capability.

No. No 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 % ChgC 3.25 3.30 3.23 3.51 3.10 3.60 3.65 3.50 3.40 3.35 3.48 3.50 3.25 3.60 3.55 3.60 3.55 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 % ChgC 3.48 3.42 3.40 3.50 3.78 3.70 3.50 3.45 3.75 3.52 3.10 3.25 3.40 3.20 3.45 3.30