Type 3 Likelihood Ratio Test

The incremental statistic for that model, and the full model (that includes all effects), then provides a test of the increment in the log-likelihood, attributable to the respective (current) effect, while controlling for all other effects.

When the model is not full-rank, that is, redundant columns are detected during the evaluation of the design matrix, some difficulties arise when computing the Wald statistic for the overall model, and when attempting to compute Type 3 LR test of effects.

Specifically, because of the redundancy of some of the parameters in the model, independent tests of effects, controlling for all other parameters in the model (not belonging to the effect under consideration), cannot be computed. Therefore, the Summary of all effects and Type 3 LR test buttons are not available in that case.