\begin{Schunk}
\begin{Sinput}
 plot(RATINGS ~ GRIP, data=dat, xlab="Grip Strength", ylab="Supervisor Rating", ylim = c(1,1.2)*range(dat$RATINGS))
 abline(mod1)
 newdf <- data.frame(GRIP=plotSeq(dat$GRIP, 20))
 pconf <- predict(mod1, interval="confidence", newdata=newdf)
 lines(newdf$GRIP, pconf[ ,"lwr"], lty=2, col="red")
 lines(newdf$GRIP, pconf[ ,"upr"], lty=2, col="red")
 ppred <- predict(mod1, interval="prediction", newdata=newdf)
 lines(newdf$GRIP, ppred[ ,"lwr"], lty=4, col="green")
 lines(newdf$GRIP, ppred[ ,"upr"], lty=4, col="green")
 legend("topright", legend=c("predicted","conf. int.","pred. int."), lty=c(1,2,4), col=c("black", "red","green"))
\end{Sinput}
\end{Schunk}
