Hi, I'm fitting a model for two-nested binay data in glmmPQL function but I have this error message: "Error in solve.default(estimates[dimE[1] - (p:1), dimE [2] - (p:1), drop = FALSE]) : system is computationally singular: reciprocal condition number = 1.14416e-018". How do I can solve this problem? Or the problem are the data? Thanks, Pedro A. Torres S. Graduate Student - Statistics Department of Mathematics University of Puerto Rico at Mayaguez (1 787) 832-4040 X 2537