I conducted an experiment with a system that allows to perform a task on a test-object using several methods. The quality of how the task was performed is measured by an error.
I measured the errors of 10 methods each conducted by 5 users on 2 test-objects whereas each user conducted 6 attempts per method and test-objects.
I would like to model this setup using a linear mixed effects model. In particular, I would like to evaluate whether there are (significant) differences
- between users (intrauser reliability)
- within users (interuser reliability)
- across test-objects (across test-object reliability)
- between methods
I think I have
- fixed effects: method
- random effects: user, test-object
Accordingly, the model would be
error ~ methods + (1|user) + (1|test-object)
Is that correct?
Furthermore, how can I know if I have a nested structure? Accordingly I would require a term like