Dear All I have a repeated measures design in which abundance was measured repeatedly over 10 months in three treatments (Tortoise A; Tortoise B and control) established in 6 blocks, i.e. crossed fixed effects. My original design incorporated two tortoises per treatment, however as fieldwork goes I ended up losing some animals. Rather than lose a couple of enclosures in the analysis and have to do a lmer, I thought I could include tortoise weight as an explanatory variable. For my treatments, tortoise weight in the control always = 0, while in general Tortoise A is twice as large as Tortoise B except when I lost animals. Is this the correct model? aov(Tel.ab~Tort.W+Treatment*Month+Error(Month/Block)) Or should tortoise weight be nested in Treatment, i.e not included as a fixed factor but including the fact that tortoises species may have an effect? I am utterly confused now as to whether that should be the case as to some extent Tort.W and Treatment are correlated. Any help would be much appreciated. Many thanks Christine ---------------------- Christine Griffiths School of Biological Sciences University of Bristol Woodland Road Bristol BS8 1UG Tel: 0117 9287593 Fax 0117 925 7374 Christine.Griffiths at bristol.ac.uk http://www.bio.bris.ac.uk/research/mammal/tortoises.html