i am comparing body-measyrments of two groups of fish that are fed different diets against each other. the problem is that the two diets lead two very different growt; one grow quickly and the other slowly. thus, the variance of body length (one of the predictor variables) are unequal unless i log-tramsform. the other predictor variable is type of diet. the response variable are other body measurments, i.e. jaw and eye length. when i do levene's test on the response variable i get a significant difference between the two diets (after trasnformation). however, when i plot the residuals agaisnt the fitted values (after transfoming both the response and the predictor variable) the variance seem okay.

so my question is; do i have to perfom a leven's test to show that the variance is equal or can i refer to the plotting of the model when i say that the data are not violating the assumptions of ANCOVA.

thank you so much for ur answer

Regards, mia