I have 2 groups (tinnitus sufferers and controls) who are significantly different in age - I would normally control for age as a covariate (as it is a cognitive task) but it violates the assumption of ANCOVA in that the independent variable and covariate are related (as expected, older people are more likely to suffer tinnitus so this difference is expected).
I am worried that putting in age as a covariate removes my group effect because age and group are too closely related for them both to be in the model - can I legitimately not include this as a covariate based on this?