I've done a SLR and after testing the residuals for normality using the Shapiro-Wilk test and I've learned that the residuals are not normal. What does this mean? Is the test useless or can it be saved? Should I use another test to test my two variables?
First of all, I wouldn't take the results of Shapiro-Wilk test as gospel. Instead, or together with S-W, I will use a Q-Q plot to visually inspect the normality of residuals.
Usually, ANOVA is pretty robust to non-normality.
If the residuals are not normal, this means the data is slightly heavier tailed or skewed (which depends on the shape of the Q-Q plot).
Usually a log transformation does the trick.
Okay, so my problem is that I've already transformed my data. I've never worked with anova before, but I'll give it a try. Is it possible to make some sort of graphical representation as with regression? I had such a pretty line in my regression when doing a scatterplot with fitted line.