For all other studies, we imputed plausible correlation values taken from averages reported in other relevant studies in the literature that tested or evaluated food safety knowledge, attitude, or behaviour questionnaires in similar populations and contexts [ 36, 40– 40].
The proportion of markers correctly imputed and correlations between true and imputed genotypes for different values of D are in Figure 1a, and the correlations for different values of T and MAF thresholds are in Figure 1b.
We calculated change and its variance using a standard formula, 30 imputing a correlation coefficient taken from one of the largest studies included in the review (see appendix 1).
37 52 56 63 68 69 The coefficients were consistent, and we imputed an intracluster correlation coefficient of 0.002 for all studies in which clustering was not considered in the original analysis.
However, for RCTs and NRTs of continuous behaviour outcomes, and for all uncontrolled before-and-after study continuous outcomes, sensitivity analyses revealed that selection of the imputed pre-post correlation in some cases changed the significance of estimates or changed estimates by >20%% (Additional file 12).
(XLS 31 kb) Additional file 11: Sensitivity analysis of imputing different correlations for combining multiple outcome measures within a study.
Two measures were used to assess imputation accuracy, the proportion of correctly imputed genotypes and the correlation between true and imputed genotypes.
For each individual, imputation accuracy was calculated using the same two measures: (i) the proportion of all of the horses' genotypes that were correctly imputed; and (ii) the correlation between the true and imputed genotypes across all the horses' SNPs when coded as above.
Missing predictor values (2% of all required values) were imputed based on the correlation with the other predictor variables (He and Shen, 1997).
