

   HHeeaadd DDiimmeennssiioonnss iinn BBrrootthheerrss

   AArrgguummeennttss::

         l1: The head length of the eldest son.

         b1: The head breadth of the eldest son.

         l2: The head length of the second son.

         b2: The head breadth of the second son.

   SSUUMMMMAARRYY::

        The `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.

   DDAATTAA DDEESSCCRRIIPPTTIIOONN::

        This data frame contains the following columns:

   SSOOUURRCCEE::

        The data were obtained from

        Frets, G.P. (1921) Heredity of head form in man. Genet-
        ica, 3, 193.

   OOTTHHEERR RREEFFEERREENNCCEESS::

        Davison, A.C. and Hinkley, D.V. (1997) Bootstrap Meth-
        ods and Their Application. Cambridge University Press.

        Whittaker, J. (1990) Graphical Models in Applied Multi-
        variate Statistics.  John Wiley.

