Let X be a real-valued wide sense stationary process over a finite non-abelian group G. We provide results on optimal orthogonal decomposition of X into real-valued mutually orthogonal components and using this decomposition we develop a test for correlation of X over the group G. Applications of these results to the analysis of variance of the carry-over effects in the cross-over designs in clinical studies are given. Our focus will be on groups S[subscript 3], S[subscript 4], and A[subscript 4].
