Stat > DOE > Taguchi > Analyze Taguchi Design > Options
Select the signal-to-noise goal for the response and whether to use the natural log transformation to stabilize the variability of the standard deviations.
Dynamic signal-to-noise ratio
For dynamic designs, you can specify a response reference value and signal value through which the regression line should pass. Or, you can choose to fit lines with no fixed reference point.
Fit all lines through a fixed reference point: In Response reference value, enter the desired output (response) value. In Signal reference value, enter the signal factor level for the desired response reference value.
Fit each line through the average response at: In Signal reference value, enter a signal factor level at which to calculate the average response for each regression line.
Fit lines with no reference point: Choose to fit the regression line with no fixed reference point. In this case, the intercept will be fitted to the data.
Use the natural logarithm transformed standard deviations as the response variable in the response table, regression/ANOVA results, and on the main effects and interactions plots.
Consider using the natural log transformation on the standard deviation for the following reasons:
To stabilize the variability of the standard deviations
To avoid negative values for the fitted values, which can occur when using untransformed standard deviations. With a log transformation, all fitted values are positive, which makes them easier to intuit.
To avoid multiplicative effects on variability. Using this option transforms multiplicative effects into additive effects, which are better suited to linear models.