The use of orthogonal comparisons within an analysis of variance is a common method of multiple comparisons. The general field of multiple comparisons considers how to analyze a multitreatment experiment to answer the specific questions of interest to the experimenter. Orthogonal comparisons are appropriate when the researcher has a clearly defined, independent set of research hypotheses that will constitute the only analyses done on the treatment means. Of the multiple comparison techniques available with comparable control over Type I error (rejecting a true null hypothesis), a set of orthogonal comparisons will provide a more powerful approach to testing differences that may exist between the treatment groups than those that are more exploratory in nature and thus more extensive. The power is gained by restricting the ...