\begin{Schunk}
\begin{Sinput}
 #newdf <- data.frame(schtype = levels(dat$schtype))
 #newdf$schtype <- relevel(newdf$schtype, "public") ###WOW:  problem required this
 plot(gradrate ~ schtype, data = dat, xlab = "Private or Public?", ylab = "Graduation Rate", ylim = range(dat$gradrate, na.rm = TRUE))
 gradratehat <- predict(mod1, interval="conf", newdata=newdf)
 lines(gradratehat[ , 1] ~ schtype, data = newdf, col = "black", lty = 1)
 lines(gradratehat[ , 2] ~ schtype, data = newdf, col = "red", lty = 4)
 lines(gradratehat[ , 3] ~ schtype, data = newdf, col = "red", lty = 4)
\end{Sinput}
\end{Schunk}
