Correlation between specificity values calculated from different datasets. All x-axes: scores from binding data from the Ambit kinase dataset . All y-axes: scores from activity data measured on the same compounds at Millipore. We calculated (in Microsoft Excel, for panels from left to right) the R-squares from linear regression as: 0.93, 0.92, 0.99, 0.54, 0.81 and the correlation coefficients as: 0.81, 0.90, 0.75, 0.57, 0.63. The straight line represents the ideal case of specificity values being insensitive to profiling method. The total squared distance of (normalized) data points to the straight line is given in the top left corner of each panel. For this latter calculation, data were normalized by dividing all values by the highest value in their set. Because the K
-Gini values are very unevenly distributed, the lowest value 0.93 was first subtracted from all data in this set. Irrespective of statistical method, the selectivity entropy, S(3 μM) and K
-Gini are the most robust metrics.