Modeling and Multivariate Methods - SAS

98 Fitting Standard Least Squares Models Chapter 3
Factor Profiling
6. Click Run.
7. From the red triangle menu next to Response Y, select Factor Profiling > Cube Plots.
Figure 3.35 Cube Plots
To change the layout so that the factors are mapped to different cube coordinates, click one of the factor
names in the first cube and drag it to the desired axis. For example, in Figure 3.35, if you click T and drag it
over Ct, then T and Ct (and their corresponding coordinates) exchange places. When there is more than one
response, the multiple responses are shown stacked at each vertex.
Box Cox Y Transformations
Sometimes a transformation on the response fits the model better than the original response. A commonly
used transformation raises the response to some power. Box and Cox (1964) formalized and described this
family of power transformations. The formula for the transformation is constructed so that it provides a
continuous definition and the error sums of squares are comparable.
y λ – 1
Y ( λ)
---------------- if λ ≠ 0
= λ – 1
λy· y·
ln ( y)
if λ = 0
where y·
is the geometric mean
The plot shown here illustrates the effect of this family of power transformations on Y.