ducks data frame has 11 rows and 2 columns.Each row of the data frame represents a male duck who is a second generation cross of mallard and pintail ducks. For 11 such ducks a behavioural and plumage index were calculated. These were measured on scales devised for this experiment which was to examine whether there was any link between which species the ducks resembled physically and which they resembled in behaviour. The scale for the physical appearance ranged from 0 (identical in appearance to a mallard) to 20 (identical to a pintail). The behavioural traits of the ducks were on a scale from 0 to 15 with lower numbers indicating closer to mallard-like in behaviour.
data(ducks)Larsen, R.J. and Marx, M.L. (1986) An Introduction to Mathematical Statistics and its Applications (Second Edition). Prentice-Hall.
Sharpe, R.S., and Johnsgard, P.A. (1966) Inheritance of behavioral characters in $F_2$ mallard x pintail (Anas Platyrhynchos L. x Anas Acuta L.) hybrids. Behaviour, 27, 259-272.