is about is_specified_input_of effect size estimate standardized mean difference strictly standardized mean difference Orlaith Burke Alejandra Gonzalez-Beltran Philippe Rocca-Serra SSMD http://en.wikipedia.org/wiki/SSMD http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2789971/ http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2789971/ strictly standardized mean difference (SSMS) is a standardized mean difference which corresponds to the ratio of mean to the standard deviation of the difference between two groups. SSMD directly measures the magnitude of difference between two groups. SSMD is widely used in High Content Screen for hit selection and quality control. When the data is preprocessed using log-transformation as normally done in HTS experiments, SSMD is the mean of log fold change divided by the standard deviation of log fold change with respect to a negative reference. In other words, SSMD is the average fold change (on the log scale) penalized by the variability of fold change (on the log scale). For quality control, one index for the quality of an HTS assay is the magnitude of difference between a positive control and a negative reference in an assay plate. For hit selection, the size of effects of a compound (i.e., a small molecule or an siRNA) is represented by the magnitude of difference between the compound and a negative reference. SSMD directly measures the magnitude of difference between two groups. Therefore, SSMD can be used for both quality control and hit selection in HTS experiments. hit selection ready for release