Zero random effect variance?

If that is the issue (which after looking back at my boxplot is probably 
the case) should I still expect literally zero variance attributed to 
the chambers?

Yes. The within-chamber intraclass correlation is -0.0835  (SE=0.0309) 
using the pairwise estimator.

| David Duffy (MBBS PhD)
| email: David.Duffy at qimrberghofer.edu.au  ph: INT+61+7+3362-0217 fax: -0101
| Genetic Epidemiology, QIMR Berghofer Institute of Medical Research
| 300 Herston Rd, Brisbane, Queensland 4006, Australia  GPG 4D0B994A