But do I need to be careful with ratio data because this essentially treats two related variables (golgi size and cell size) as a single variable. Are there more suited methods to explore this data?

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But do I need to be careful with ratio data because this essentially treats two related variables (golgi size and cell size) as a single variable. Are there more suited methods to explore this data?

I'm now wondering whether ANCOVA is the way to go with this with Golgo area as the independent *dependent *variable and cell area as a covariate *with genotype as an independent variable*. Thoughts?

Is there any theory or reason to believe that, for a given cell size, the relationship between golgi size and genotype changes? In other words, is it reasonable to assume that the relationship between golgi size and genotype is modified by overall cell size (or that relationship of golgi size with cell size is modified by genotype)?

EDIT: I may need to clarify-- are you trying to look at total cell size or size of the golgi apparatus? My reply assumed (possibly incorrectly)that you were interested in the golgi size. If you're interested in total cell size as the dependent variable, then switch "golgi" and "total cell" in my reply.

Turns out that my model violates some the assumptions of ANCOVA (numbers 3 and 4 in the link). In particular the covariate, cell area, is different between some of the genotypes. The variances are also not equal.

I am a little confused because if there is a difference between cell size and not a difference in golgi size, then I would expect a difference in the ratio of golgisize/cellsize, but this is not the case.

I am unsure how to proceed.

The more statistical tests I perform the more likely I am to find one that 'looks good', which I want to avoid.