A multitude of factors affect power, including the combination of variance components used in the model, heritability effect size (ranging between 0 and 1), sample size and the proportion of monozygotic (MZ) to dizygotic (DZ) twins in the dataset.
Multivariate analysis was used to separate the phenotypic variance of individuals into additive genetic (heritability) effect (A), shared (family) environment (C), and non-shared (individual-specific) environment (E).
Based on a previously published simulation study on the power of twin studies36, our sample size surpasses the minimum requirements for having 95% power of rejection of the false - zero heritability - hypothesis at the 5% significance level even when the true heritability effect is as low as 0.3.
By assuming the existence of only additive genetic effects in the twin model, a previous simulation study reported minimum required sample sizes ranging between 75 and 2,000 twin pairs in order to achieve 95% statistical power, depending on heritability effect sizes ranging from 0.8 to 0.2 respectively, and keeping the MZ to DZ ratio close to one36.
Estimates of heritability, litter effects, and phenotypic and genetic correlations for VL and WG are in Table 2.
In LD mapping, for example, many simulation studies have been carried out to obtain the optimal experiment design to detect QTLs, by considering a wide range of parameters, such as population size, number of markers, heritability and effects of QTLs, length of LDs, and the number of generations.
Over roughly the same period of time, the salmon aquaculture industry and the salmonid hatchery 'industry' generated numerous papers pertaining to selection responses, trait heritability, temperature effects on myriad characteristics and genetic differentiation (e.g. references cited by Mousseau and Roff 1987; Purdom 1993).
The heritability-level effects of FcritBB on the microevolutionary patterns of FcritBB were analyzed by comparing scenario B (h = 1) to scenario G (h = 0.6).
A number of scenarios were simulated with different power to identify QTL by varying family size, heritability, QTL effect and map density, and three threshold levels for cofactor were considered.
Clearly, if a risk factor has strong heritability, beneficial effect of any intervention can only be successful if it is implemented in early adulthood or, even better, in early childhood.
