Hp. Kohler et Jl. Rodgers, DF-like analyses of binary, ordered, and censored variables using probit and tobit approaches, BEHAV GENET, 29(4), 1999, pp. 221-232
Binary and censored variables can lead to erroneous inferences about herita
bility in family studies if the dichotomous or censored nature of the depen
dent variable is not properly accounted for. The bivariate probit and tobit
models proposed in this paper provide a unified approach to family studies
with binary, ordered, and censored variables. Each model in this paper is
derived from a similar latent-variable structure which can contain covariat
es that affect the expected value of the dependent variable, as well as gen
etic and shared environmental influences that lead to an association among
related individuals. We apply the models to the fertility outcome and ferti
lity motivations of Danish twins born 1953-1964 and find relevant genetic i
nfluences on the number of children as well as the desired timing of the fi
rst child.