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.

• 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 (e.g. Fraction defective).

  • Use Logit for data that approaches but never quite reaches boundary conditions (e.g. yield, shrinkage). The boundary conditions must be entered.