[R] which test for seven groups with dependency in replication and discrete values

[Ralph Scherer]

hello!

My Problem is, that I want to compare seven groups, which have the 
discrete values from 0 to 3. These are damageclasses of plants. 0 is 
best and 3 is worst. Every group has 4 replications with 2 plants. The 
two plants were together in a cage with animals. I think the problem is 
that the two plants are not independent from each other. I don't know 
which test I can use for this problem. I thought the chisquare test but 
I can't find it for more than two groups and I don't know how I should 
consider the dependence between the two plants of every replication. I 
want to find out if there are significantly differences between the 
groups. I hope someone could help me.

Thanks and greetings,
Ralph