Transformation¶
Unless previous knowledge supports applying a transformation, leave the Transformation set to “None”. Come back to the Transformation tab if there are indications in the analysis and diagnostics that a data transformation is required.
Towards the bottom of this screen, look at the ratio of the maximum to minimum response - larger ratios indicate a higher likelihood that a transformation may help the analysis.
Once a transformation is selected use the Constant “k” entry box to add a constant to the response data. Transformations require all positive data.
Most of the time a common Power Law transformation will be appropriate. Power law transformations raise the response data to the specified power. The one labeled Power can be used to pick a custom exponent.
The last two options are non-power law transformations. They will not be suggested by the analysis or diagnostics.
Use ArcSine Square Root for proportion data between 0 and 1 (eg. Fraction defective).
Use Logit for data that approaches but never quite reaches boundary conditions (eg. yield, shrinkage). The boundary conditions must be entered.
Options Button:¶
Fit Summary¶
Max Process Model Order: For very large designs it can take a great deal of time to compute all the possible model orders for the fit summary. This option can be used to limit the computations to lower-order models to save time. If higher-order models are necessary, they can still be fit on the model screen.
Analysis¶
Coding for Analysis: Coding for Analysis: For most analysis use the Coded setting. The Actual setting computes the least squares fit using the factor settings as entered. Advanced modeling techniques require fitting a model in the actual scale or real scale for mixtures.