Latin square
= Latin square
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A Latin square of order $q$ is a $q\times q$ array of $q$ symbols, each occurring once in each row and column. Used as a <row-column design>, its symbols label <treatments>. Centered <treatment> indicators are <orthogonal> to both row and column indicators, because every row-treatment and column-treatment pair occurs once. This balance separates additive effects from two nuisance directions.