Revista Colombiana de Estadística
Print version ISSN 0120-1751
HOOKS, TISHA et al. Analysis of Covariance with Spatially Correlated Secondary Variables. Rev.Colomb.Estad. [online]. 2008, vol.31, n.1, pp. 95-109. ISSN 0120-1751.
Advances in precision agriculture allow researchers to capture data more frequently and in more detail. For example, it is typical to collect "on-the-go" data such as soil electrical conductivity readings. This creates the opportunity to use these measurements as covariates for the primary response variable to possibly increase experimental precision. Moreover, these measurements are also spatially referenced to one another, creating the need for methods in which spatial locations play an explicit role in the analysis of the data. Data sets which contain measurements on a spatially referenced response and covariate are analyzed using either cokriging or spatial analysis of covariance. While cokriging accounts for the correlation structure of the covariate, it is purely a predictive tool. Alternatively, spatial analysis of covariance allows for parameter estimation yet disregards the correlation structure of the covariate. A method is proposed which both accounts for the correlation in and between the response and covariate and allows for the estimation of model parameters; also, this method allows for analysis of covariance when the response and covariate are not colocated.
Keywords : Covariance Analysis; Spatial Analysis; Cokriging; Covariate.