|
White Paper
PROCESS CAPABILITY METRICS
Determining Confidence Intervals for the Z-score
"We’re two Sigma." "We’re three Sigma." "We’re negative Sigma."
Good or bad, I always see a look of satisfaction in the face of a new Black Belt the first time that they calculate the "Sigma level" for their process. As the namesake for the Six Sigma initiative, new practitioners are always drawn to the Sigma level metric when studying capability analysis for the first time. Prior to embarking on a capability study, students of Six Sigma should also be taught the importance of validating the integrity, relevance, accuracy and precision of the metrics and measurement system that they are using to draw conclusions and make recommendations. So it is only fitting that the validity of the Sigma-level metric be understood as well. To accomplish this we will determine the confidence interval for the Sigma level as an assessment of its precision. As we will see, a significant level of uncertainty can exist in your Sigma-level metric depending on how you carry out your capability analysis.
Full White Paper>> [PDF:173K]
|
