Greco-Latin square designs

The Greco-Latin square design involves two Latin squares that are superimposed on each other. It contains two treatment factors instead of one and contains four factors overall instead of three. An example design would look as follows ... 

The analysis for the Greco-Latin square design is similar to that of a Latin square design. However, one noticeable difference is that two treatment sum of squares have to be computed (factors C and D) by listing two sets of means outside the design table. As an additional note, Greco-Latin squares are most effective if replicated and are subject to the same randomization rules as for the Latin squares. 

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