Modified tests of independence in 2x2 tables with spatial data

In this paper we suggest two modified chi-squared tests of independence in 2 x 2 tables when the data are spatially autocorrelated. For this purpose, we first derive the asymptotic distribution of standard test statistics based on the sample cross-product ratio under mild conditions on the nature of spatial dependence. The performance of the tests is assessed by means of a Monte Carlo experiment in a lattice case. From simulation results, the need to adjust standard test statistics is apparent when spatial autocorrelation is present in both variables. An illustrative application to ecological data is also given.