I'm pretty new to R and I have a stats problem that's got me baffled. I'm trying to carry out a repeated measures test on Poission distributed data, where half the subjects in each block (4 blocks) were treated, and half were controls. Measurements were carried out before and after the treatment. There was another 2-level factor included. The trouble is I can't take averages, and have to include the identity of each subject in each block. Can anyone help? Andy Higginson This message has been scanned but we cannot guarantee that it and any attachments are free from viruses or other damaging content: you are advised to perform your own checks. Email communications with the University of Nottingham may be monitored as permitted by UK legislation.