\name{Rail}
\alias{Rail}
\title{Evaluation of Stress in Railway Rails}
\description{
    The \code{Rail} data frame has 18 rows and 2 columns.
}
\format{
    This data frame contains the following columns:
    \describe{
	\item{Rail}{
	    an ordered factor identifying the rail on which the
	    measurement was made.
	}
	\item{travel}{
	  a numeric vector giving the travel time for ultrasonic
	  head-waves in the rail (nanoseconds).  The value given is the
	  original travel time minus 36,100 nanoseconds.
	}
    }
}
\details{
  Devore (2000, Example 10.10, p. 427) cites data from an article in
  \emph{Materials Evaluation} on ``a study of travel time for a certain
  type of wave that results from longitudinal stress of rails used for
  railroad track.''
}
\source{
    Pinheiro, J. C. and Bates, D. M. (2000), \emph{Mixed-Effects Models in S
	and S-PLUS}, Springer, New York.  (Appendix A.26)

    Devore, J. L. (2000), \emph{Probability and Statistics for
      Engineering and the Sciences (5th ed)}, Duxbury, Boston, MA.
}
\examples{
str(Rail)
(fm1 <- lmer(travel ~ 1 | Rail, Rail))
}
\keyword{datasets}