part of is about is model for data item statistical model covariance covariance structure Orlaith Burke Tom Nichols http://www3.nd.edu/~kyuan/courses/sem/readpapers/benter.pdf Philippe Rocca-Serra Camille Maumet Alejandra Gonzalez-Beltran a covariance structure is a data item which is part of a regression model and which indicates a pattern in the covariance matrix. The nature of covariance structure is specified before the regression analysis and various covariance structure may be tested and evaluated using information criteria to help choose the most suiteable model regression model covariance matrix metadata complete