I am dealing with process capability matrices for validation purpose. I am bit confuse with one of my process validation batch results.
Following are the results and specs. I did some basic calculation but there is some confusion if some one can help me out…
USL - 1.35
LSL - 1.11
Observation Results - 1.15, 1.15, 1.16, 1.15, 1.15, 1.16, 1.15, 1.15, 1.16
Mean - 1.1533
Std Dev - 0.005
Cp = (1.35 - 1.11/ 6 * 0.005)
= 8
CpK = Min (1.35 - 1.1533/ 3 * 0.005, 1.1533 - 1.11/ 3 * 0.005)
= Min (13.11, 2.88)
CpK = 2.88
After reading materials for capability index, it was clear that value above 2 for Cp and CpK is great. Process has achieved 6 sigma capability.
But as we see my results are towards Lower Specification Limit. All datas are skewed towards left of the plot.
Does still my process is known as 6 sigma capable?
Or
My calculation is wrong?
Please clarify.
Thanks,
Bharat