20 February 2011 by Fang Zhou
Correlation and Variation
Six Sigma projects differ from traditional projects in one important requirement – understanding of the Y=f(x) relationship with data before developing or implementing a solution. In the DMAIC framework, we identify, test and verify the causal relationship between a potential root cause (x) and the outcome (Big Y), and then develop a solution to change the x to move the Y in the desired direction. This sounds simple enough. But in practice, why is it so hard to identify and/or verify such relationships? Is the concept of hypothesis testing too difficult? Are statistical tools too complicated for the average person? Maybe. But before we teach people statistical tools, we have to first help them develop statistical thinking – the concept of variation. All the statistical tools would be unnecessary if there were no variation in life. So how does variation affect our ability to understand Y=f(x)?  read it on: http://networkedblogs.com