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Design of Experiments - US Army Conference on Applied Statistics

Design of Experiments - US Army Conference on Applied Statistics

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Orthog<strong>on</strong>al Coding and Orthog<strong>on</strong>al <str<strong>on</strong>g>Design</str<strong>on</strong>g><br />

1. Dummy columns for categorical factors are orthog<strong>on</strong>ally coded if their<br />

dot product is zero.<br />

a) The column means are zero.<br />

b) The pairwise column correlati<strong>on</strong>s are zero.<br />

2. For the purpose <str<strong>on</strong>g>of</str<strong>on</strong>g> this course we say that a design is orthog<strong>on</strong>al if:<br />

a) The means <str<strong>on</strong>g>of</str<strong>on</strong>g> the columns <str<strong>on</strong>g>of</str<strong>on</strong>g> the design matrix are all zero.<br />

b) The pairwise correlati<strong>on</strong> for all column pairs <str<strong>on</strong>g>of</str<strong>on</strong>g> the design matrix are zero.<br />

c) So, whether a design is orthog<strong>on</strong>al can depend <strong>on</strong> the model you fit.

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