Head Dimensions in Brothers

SUMMARY:
       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.

DATA DESCRIPTION:
       This data frame contains the following columns:

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.

SOURCE:
       The data were obtained from

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

OTHER REFERENCES:
       Davison, A.C. and Hinkley, D.V. (1997)  Bootstrap  Methods
       and Their Application. Cambridge University Press.

       Whittaker,  J.  (1990)   Graphical   Models   in   Applied
       Multivariate Statistics.  John Wiley.