Fluxes were approximated by dividing differences in two concentrations by the experiment time (4 hours), and standard errors for fluxes were derived by adding the variances of the two concentration measurements.
Testing for pure specification bias by adding the variances of the LGA mean THM concentrations to the models reduced the IRRs in men somewhat but had little effect on women (Table 3).
Estimates of the individual log variances associated with each of the eight variables are developed from a regression model based on the assumptions of log normality and that the total variance can be obtained by adding the variances associated with each individual variable (Hattis et al. 1999).
One technical reason could have been a strong increase in statistical variance in the ischemic samples caused by adding the experimental variance to the basic biological fluctuation between individual mice, and thus strongly decreasing power for the detection of differences.
This was further augmented by adding the sandwich variance estimate (Lin 1994) to adjust for correlated observations within each airshed.
The use of the Cox regression procedure for estimating PRs gives wider than adequate CIs [ 35], which was corrected for in the cross-sectional analysis by adding the robust variance option.
Variances for the interference profiles were obtained by adding the scaled variances of the constituent profiles.
We combined the results of these regressions, separately for the uncorrected and size-corrected data, by adding the amount of variance explained by the SEVM regression on each component, weighted by the corresponding proportion of variance explained by each principal component.
Because Poisson and non-Poisson variance are independent from one another (Additional File 1, Figure S12), total variance can be calculated by adding the independent components of the variance [ 39].
For the GRS models, we calculated adjusted R, with and without the GRS to determine the explained variance, by adding the GRS in the models for each racial/ethnic group.
