I am considering an ANOVA model for such data:
Student Class Points on exam Day of studying
1 P1 12 Day 10
2 P3 23 Day 5
3 P3 8 Day 1
4 P2 36 Day 10
5 P1 10 Day 1
6 P2 86 Day 10
7 P1 13 Day 5
...
and such ANOVA model:
model <- aov(Points ~ Class + Day, data)
ggqqplot(residuals(model))
how can I check if this model satisfies the normality of distribution? (other than the Q-Q plot of the model?)
My Q-Q plot of the model (above) seems to show normal distribution but when I perform Shapiro-Wilk( that considers only Points) the p-value comes out incredibly small... Therefore I don't know if I can assume the normality or not.
Shapiro-Wilk normality test
data: Points
W = 0.92212, p-value = 9.97e-13
Points
and at least 3 classes and at least 3 days. Unless the distribution ofPoints
is. conditional, on predictor, very skewed I doubt there is a strong case for doing anything different. The threads cited by @Tim are helpful here. $\endgroup$