Taking the median parameter values from the 101 data sets, the simulated latent data correlated 0.72 in MZ twins and 0.36 in DZ twins, just as would be expected. The sum scores correlated 0.45 in MZ twins and 0.21 in DZ twins (medians of the 101 data sets) and the log-transformed sum scores correlated 0.41 and 0.20, respectively. Thus, twin correlations are severely attenuated when analysing sum scores, even with 14 items.
