Articles |
Model diagnostic tests for selecting informative correlation structure in correlated data
Department of Statistics, University of Illinois at Urban-Champaign, Champaign, Illinois 61820, U.S.A. anniequ{at}illinois.edu
Department of Biostatistics, University of Texas, M.D. Anderson Cancer Center, Houston, Texas 77030, U.S.A. jjlee{at}mdanderson.org
Department of Statistics, The Pennsylvania State University, Pennsylvania 16802, U.S.A. bgl{at}psu.edu
Received for publication 1 August 2006.
Revision received 1 March 2008.
| Abstract |
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In the generalized method of moments approach to longitudinal data analysis, unbiased estimating functions can be constructed to incorporate both the marginal mean and the correlation structure of the data. Increasing the number of parameters in the correlation structure corresponds to increasing the number of estimating functions. Thus, building a correlation model is equivalent to selecting estimating functions. This paper proposes a chi-squared test to choose informative unbiased estimating functions. We show that this methodology is useful for identifying which source of correlation it is important to incorporate when there are multiple possible sources of correlation. This method can also be applied to determine the optimal working correlation for the generalized estimating equation approach.
Key Words: Cancer prevention Chi-squared test Generalized estimating equation Generalized method of moments Goodness-of-fit test Information matrix test Model selection Quadratic inference function Working correlation