Survey of features associated with the achievement of higher efficacies. The efficacy of a siRNA experiment is rated on a four-level scale. In Set A, the percentages of records achieving these ratings are 34.1%, 34.6%, 16.3% and 14.9%, respectively. The distribution of the efficacy ratings across the four levels changes when certain feature is present in the siRNA experiments. For 14 selected features (they constitute 7 pairs of "complementary features"), the efficacy rating distributions of the subpopulations of siRNA experiments carrying these features are presented. Dotted vertical lines extend from the distribution of the general population.