Analysis of Repeated Measures Data Ramon C. Littell

Effect on growth regulators on chrysanthemum plantsData courtesy James Barrett and Terril NellMixed Model Repeated Measures AnalysesSelecting a Covariance StructureEstimated R Matrix for plt(blk*chem) 1 1 bonziRow Col1 Col2 Col3 Col4 Col5 Col61 22.0547 19.3033 14.4120 9.7663 7.1461 8.95522 19.3033 22.0547 19.3033 14.4120 9.7663 7.14613 14.4120 19.3033 22.0547 19.3033 14.4120 9.76634 9.7663 14.4120 19.3033 22.0547 19.3033 14.41205 7.1461 9.7663 14.4120 19.3033 22.0547 19.30336 8.9552 7.1461 9.7663 14.4120 19.3033 22.0547Estimated R Correlation Matrix forplt(blk*chem) 1 1 bonziRow Col1 Col2 Col3 Col4 Col5 Col61 1.0000 0.8752 0.6535 0.4428 0.3240 0.40602 0.8752 1.0000 0.8752 0.6535 0.4428 0.32403 0.6535 0.8752 1.0000 0.8752 0.6535 0.44284 0.4428 0.6535 0.8752 1.0000 0.8752 0.65355 0.3240 0.4428 0.6535 0.8752 1.0000 0.87526 0.4060 0.3240 0.4428 0.6535 0.8752 1.0000Fit Statistics-2 Res Log Likelihood 502.6AIC (smaller is better) 514.6AICC (smaller is better) 515.5BIC (smaller is better) 520.6Interpretation:The “toep” and “unstructured” correlation matrices are similar, but the covariance matricesare quite different due to heterogeneous variances, which are not accommodated by “toep.”The AICC fit index is 515.5 and the BIC fit index is 520.6 for toep, both larger than for arh(1).This indicates using the arh(1) covariance structure.