**General Linear Model for a Latin Square:**

In design of experiment, a Latin square is a three-factor experiment in which for each pair of factors in any combination of factor values occurs only once.

Consider the following Latin Square,

where rows correspond to 4 values of factor I, columns - to 4 values of factor II, and letters to 4 values of factor III.

A general linear model for this experiment is

where Y_{ijk} are observed values of the dependent variable, are effects corresponding to the 4 values of factor I, - of factor II, - of factor III, e_{ijk} are random variations.

Note: the Latin square is appropriate only if effects of all three factors are additive - that is, all interaction effects are zero.