Notes. For each study, the table reports: the main author (column “paper”); the kind of data used (column “data”); whether a confidence strip has been computed for the skill score (column “multiple test realizations”); whether data belonging to the same AR are split between the training and test sets (column “AR data split”); whether a validation set has been used to optimize the machine learning algorithm (column “validation”); which method has been used (column “method”); and the score values for the prediction of C1+ and M1+ flares (columns “score – C1+” and “score – M1+”).