\begin{Schunk}
\begin{Sinput}
 newdf <- data.frame(schtype = factor(c("public", "private"), levels = c("public", "private")))
 gradratehat <- predict(mod1, interval = "conf", newdata = newdf)
 newdf <- cbind(gradratehat, newdf)
 newdf
\end{Sinput}
\begin{Soutput}
       fit      lwr      upr schtype
1 50.18203 48.56150 51.80256  public
2 66.10013 64.88272 67.31754 private
\end{Soutput}
\end{Schunk}
