Re: fixed effect with ancova

Posted by ro on Aug 23, 2011; 4:25pm
URL: http://spssx-discussion.165.s1.nabble.com/fixed-effect-with-ancova-tp4713723p4727317.html

Hi

i finish to check all data, then my tank numbers was reduced to 21 and 7 diets (the design was the same that before: 3 tanks by each diet), the number of fishes in each tank is variable, the minimum number of fishes in each tank is 6 but the most of tanks have 12 fishes (unbalanced?)...

i am not finish to analysis my data (all data normalized), but it appear have the same problem, i can not find tank effect and interaction and diet effect disappear, other problem is that degree of freedom (ds) in the analysis only compute 14 tanks From 21!! and 0 in diet!!...why? i did the same analysis with genstat software and compute 20 df and 6 diet (exactly the same data) and recognized diet and tank effect but no interaction... when i plot means for tank (x) and diet (y) i see interaction very clear, i thought that the problem is in diet effect, because spss dont compute diet effect...

i attach pdf with results