The calculated contributions of the

The calculated contributions of the parameters are shown in Table 7.The level average response analysis by S/N ratio is shown in Table 6 and Fig.4. Although the physical meaning of S/N ratio is not as straight forward as simple level average response analysis by values, it is more objective towards the target because the S/N ratio reflects both the average (mean) and the scatter (variance)[21]. For optimum values of the selected parameters, the level that gives the highest S/N ratio was chosen[19].