I am also a little bit confused about the assumption of independence.
I have the following situation:
- one continuous dependent variable (radiant power of a medical device)
- a few independent variables [age of the device (categorized), ...]
The researcher went to a lot of doctors' surgeries to investigate the radiant power of their device[s]. The issue is, that some practices had more than one device.
My question is whether it is still meaningful to apply a multi-factor ANOVA? Because I doubt that the observations taken from the same surgery are independent from each other.