Classifier Performance. Actual length of sequences used. Column Classifier denotes features used from the training set. TP% denotes percentage of true positives. FP1% and FP2% represent the percentages of antisense sequences and E. coli UTRs that are misclassified as riboswitches, respectively. Sensitivity denotes overall percentage of correctly classified sequences. Sig. denotes significant (less than 0.05 in the training set) features of the multinomial classifier.