I have 2 factors, one (Page type) of 2 levels and the other (Intensity) of 4 levels. I did a 2x4 Full Factorial Design with 10 replications, so I did 80 experiments. Then I wanted to do a two-way ANOVA on these data. Correct me if I'm wrong, but what I have to check is if the residuals are indipendent, homoschedastic and normally distributed.
The indipendence and the homoschedasticity is verified by the "Residual by Predicted Plot" because there are no visibile trends or increasing spreads.
The normality assumption is not verified (second plot), but it seems not a big deal because:
Furthermore, normality is the least important assumption of a linear model (e.g., an ANOVA); the residuals may not need to be perfectly normal. (https://stats.stackexchange.com/a/28635/36058)
It seems like they are almost normal.
So, are my thoughts correct? Can I correctly do a two-way ANOVA on these data?
(Full ANOVA: http://i.imgur.com/7tR3Kv2.png)