# A formula for Type III sums of squares

```@article{Lamotte2019AFF,
title={A formula for Type III sums of squares},
author={Lynn Roy Lamotte},
journal={Communications in Statistics - Theory and Methods},
year={2019}
}```
• L. Lamotte
• Published 29 March 2018
• Mathematics
• Communications in Statistics - Theory and Methods
Type III methods were introduced by SAS to address difficulties in dummy-variable models for effects of multiple factors and covariates. They are widely used in practice; they are the default method in several statistical computing packages. Type III sums of squares (SSs) are defined by a set of instructions; an explicit mathematical formulation does not seem to exist. An explicit formulation is derived in this paper. It is used to illustrate Type III SSs and their properties in the two-factor…
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