Projected autocorrelation function of X-ray galaxy groups in the ECDF-S. The red points show the results for all the groups and the black points again for groups but excluding the central area from both real and random catalogs. As we discuss in the text, we do not see any significant change in the results, after introducing the method for correcting the first order effects from cosmic variance. The dotted lines show the two-halo terms for all groups (black) and excluding the central area from the real and random group catalogs (red).