In Appendix D, Table D.14, we show data taken from Brownlee (1960) showing a response and three predictors. These data were used to illustrate the concept of variable selection. (See also Draper and Smith (1981).) The data were also used by Andrews (1974) to illustrate the robust methods discussed in Section 6.7. Daniel and Wood (1971) gave an interesting explanation for the unusual behavior of some observations. Fit a model that is linear in each of the predictors and examine the case diagnostics and plots described in this chapter to identify any unusual observations.