## References

Kitchens, L. J. (2003) *Basic Statistics and Data Analysis*.
Pacific Grove, CA: Brooks/Cole, a division of Thomson Learning.

## Examples

```
model <- lm(sat ~ psat, data = Psat)
par(mfrow = c(1, 2))
plot(Psat$psat, resid(model))
plot(model, which = 1)
rm(model)
par(mfrow = c(1, 1))
```