Modeling and Multivariate Methods - SAS

254 Performing Nonlinear Regression Chapter 9
Nonlinear Fitting with Fit Curve
Figure 9.7 Parallelism Test
The report gives the following results:
Test Results Gives the results of an F Test and a Chi-Square Test for parallelism. The F Test compares the
error sums-of-squares for a full and a reduced model. The full model gives each group different
parameters. The reduced model forces the groups to share every parameter except for the inflection
point.
Parallel Fit Parameter Estimates Gives the parameter estimates under the reduced model (same
parameters, except for inflection point). A plot of the fitted curves under the reduced model is provided.
Relative Potencies Gives the relative potencies. There is a report for each level of the grouping variable.
The potency is EC 50 for logistic models, where EC 50 is the point at which the middle response value is
obtained. For the Logistic 2P, 3P, and 4P, the potency is exp(inflection point parameter). The relative
potency is the ratio of these potencies.
Compare Parameter Estimates
The Compare Parameter Estimates report gives results for testing the equality of parameters across the levels
of the grouping variable. There is an Analysis of Means report for each parameter, which tests whether the
parameters are equal to an overall mean. If the result for a parameter exceeds the decision limits, then the
parameter is different from the overall mean. See Figure 9.8.