Theoretically, the consistency variances model is optimal in that it largely retains the flexibility of the unrestricted variances model, and additionally restricts variances in alignment with and borrows strength from the seminal assumption of consistency.
It is possible that our study was hampered by the number of centres, rather than the number of patients, that may have restricted variance.
The substantial inverse shared environmental correlations at high levels of education, however, suggested that cultural/familial influences on high educational attainment acted relatively uniformly and effectively to reduce BMI by restricting variance.
In the present study, this selection may have affected estimates of relationships between variables of interest through restricted variance.
However, a large bias due to restricted variance seems unlikely because the magnitude of the association between antidepressant use and diagnosed diabetes was comparable with that observed in other cohorts (3 10).
bIn addition, we checked whether this result was due to the restricted variances in low-performing countries and found that neither ceiling nor floor effects in the problem solving scores existed.
In fact, because education restricted environmental variance more than genetic variance, heritability, or the proportion of total variance attributable to genetic influences, was higher at high levels of education in both genders (see Table 3).
My view (simply my attempt to make head or tail of all this, not a prescription for changes) is that UPI, random segregation and bottlenecks all increase the variance between oocytes, and restrict the variance between mitochondria within the same oocyte (i.e. increase clonality).
In quantitative genetics the prediction error variance-covariance matrix is central to the calculation of accuracies of estimated breeding values (u ^ ) [ e.g. [ 1]], to REML algorithms for the estimation of variance components [ 2], to methods which restrict the variance of response to selection [ 3], and can be used to explore trends in Mendelian sampling deviations over time [ 4].
These results do not necessarily contradict each other as smaller variation in treatment procedures may restrict the variance due to individual therapists.
