\frametitle {Example of stepwise variable selection with R cont'}
{\scriptsize
\begin{block}{}
\begin{verbatim}
step.back
Start:  AIC=54.65
death.rate ~ 1 + doctor + hospital + income + pop.density

              Df Sum of Sq    RSS    AIC
- hospital     1    1.6763 124.75 53.369
- doctor       1    2.9139 125.99 53.892
<none>                     123.07 54.652
- income       1    5.0825 128.16 54.797
- pop.density  1    9.6144 132.69 56.639

Step:  AIC=53.37
death.rate ~ doctor + income + pop.density

              Df Sum of Sq    RSS    AIC
<none>                     124.75 53.369
- doctor       1    5.1882 129.94 53.529
- income       1    6.1544 130.91 53.921
- pop.density  1    8.3192 133.07 54.791
\end{verbatim}
\end{block}
}