\HeaderA{frets}{Head Dimensions in Brothers}{frets}
\keyword{datasets}{frets}
\begin{Description}\relax
The \code{frets} data frame has 25 rows and 4 columns.


The data consist of measurements of the length and breadth of the heads of 
pairs of adult brothers in 25 randomly sampled families.  All measurements
are expressed in millimetres.
\end{Description}
\begin{Usage}
\begin{verbatim}
frets
\end{verbatim}
\end{Usage}
\begin{Format}\relax
This data frame contains the following columns:


\describe{
\item[\code{l1}] The head length of the eldest son.

\item[\code{b1}] The head breadth of the eldest son.

\item[\code{l2}] The head length of the second son.

\item[\code{b2}] The head breadth of the second son.
}
\end{Format}
\begin{Source}\relax
The data were obtained from


Frets, G.P. (1921) Heredity of head form in man. \emph{Genetica}, \bold{3},
193.
\end{Source}
\begin{References}\relax
Davison, A.C. and Hinkley, D.V. (1997) 
\emph{Bootstrap Methods and Their Application}. Cambridge University Press.


Whittaker, J. (1990) \emph{Graphical Models in Applied Multivariate Statistics}.
John Wiley.
\end{References}