Dear Listers This is not a straight R inquiry. I am using R for quite a period and I wish to analyse a study with it. I am doing a survey of hepatitis C in a village. Tha unit of sampling is the house (or the family living in that house), so when a house is chosen, all the members are tested for hepatitis C antigen and viremia. How can I prove familial clustering of that infectious disease? and how to adjust for that clustering in the logistic regression? Can these be done in R?? Any help from R experts will be appreciated and any reference will be of great value. Thanks in advance. Dr Mostafa El houssinie