Table I.

Parameters of interest in Monte Carlo simulation.

Parameter	Raw	Log-scale	Ordinalized
Mean	3.33	0.94	0
Phenotypic Variance	37.04	0.88	1
MZ Covariance	24.07	0.55	0.70
DZ Covariance	18.52	0.42	0.54
MZ Correlation	0.65	0.63	0.70
DZ Correlation	0.5	0.48	0.54
Additive-Genetic Variance	11.11	0.27	0.33
Shared-Environmental Variance	12.96	0.29	0.38
Nonshared-Environmental Variance	12.96	0.33	0.29
Heritability	0.30	0.30	0.33
Shared-Environmentality	0.35	0.33	0.38

notes: MZ = monozygotic twin, DZ = dizygotic twin. Raw parameters describe the data-generating bivariate Lagrangian Poisson distributions. Log-scale parameters describe the data-generating distributions after applying a log(y + 1) transformation to the variables. Ordinalized parameters describe the data-generating distributions after they have been ordinalized to a five-point scale. To identify the ordinal model, the mean and variance must be fixed to 0 and 1, respectively. As a result, some parameters of the ordinalized distribution are redundant with one another.