Modeling and Multivariate Methods - SAS

Chapter 8 Analyzing Screening Designs 235
Tips on Using the Platform
Table 8.1 Description of the Contrasts Report (Continued)
Bar Chart Shows the t-ratios with blue lines marking a critical value at 0.05
significance.
Contrast
Lenth t-Ratio Lenth’s t-ratio, calculated as ------------------- , where PSE is Lenth’s Pseudo-Standard
PSE
Error. See “Lenth’s Pseudo-Standard Error” on page 239 for details.
Individual p-Value
Simultaneous p-Value
Aliases
Analogous to the standard p-values for a linear model. Small values of this
value indicate a significant effect. Refer to “Statistical Details” on page 238
for details.
Similar to the individual p-value, but multiple-comparison adjusted.
Appears only if there are exact aliases of later effects to earlier effects.
Half Normal Plot
The Half Normal Plot shows the absolute value of the contrasts against the normal quantiles for the
absolute value normal distribution. Significant effects appear separated from the line towards the upper
right of the graph.
The Half Normal Plot is interactive. Select different model effects by dragging a rectangle around the effects
of interest, or hold down CTRL and click on an effect name in the report.
Launching a Model
The two buttons below the Half Normal Plot construct a model using the currently selected effects. The
Make Model button opens the Fit Model launch window, which will be populated with the selected effects
and responses. The Run Model button runs the model immediately, without showing the Fit Model launch
window.
Tips on Using the Platform
Higher-Order Effects. Control-click to select more or fewer effects. The effect selection is not
constrained by hierarchy. For example, if A*B is selected, check to make sure the lower-order effects (the
A and B main effects) are also selected. Control-click to select them if they are not already selected.
Re-running the Analysis. Do not expect the p-values to be exactly the same if the analysis is re-run. The
Monte Carlo method should give similar, but not identical, values if the same analysis is repeated.
Additional Examples
This section provides examples of using the Screening platform.