```{r residuals normal, fig.height= 4}
par(mfrow=c(1,2))
hist(step2_model$residuals, main = "Residual Distribution", 
 xlab = "Residuals", col = "lightgreen")
qqnorm(step2_model$residuals, col = "blue")
qqline(step2_model$residuals, col = "red")
```