Taguchi showed to decrease the variation. with SN-ratio on 1984.
It was called Taguchi methods in USA. However, there were many estimation problems.
So, we investigated estimation accuracy by SN ratio to compare the optimum condition(b) and the experiment best (a) for case studies. Our expectation was a<b. However 62% cases were (a>b) . Taguchi way was the very poor estimation.