Page 279 - Applied Statistics with R

13.2. CHECKING ASSUMPTIONS 279

Normal Q-Q Plot, fit_2

15

10
Sample Quantiles 5 0

-10 -5
-15

-3 -2 -1 0 1 2 3

Theoretical Quantiles

For fit_2, we have a suspect Q-Q plot. We would probably not believe the
errors follow a normal distribution.

qqnorm(resid(fit_3), main = "Normal Q-Q Plot, fit_3", col = "darkgrey")
qqline(resid(fit_3), col = "dodgerblue", lwd = 2)