Same holds for Δmeanz and Δmeanmfe. Both measure the folding energy differences of the individual sequences, but do not capture identical features of the input alignment nor can be transformed into each other. The mean z-score compares the average stability of individual sequences to a random control set. Whereas the mean of minimum free energies of individual sequences specifies the actual observed minimum free energies. The difference in z-scores describes the relative loss of stability compared to a random control set. It quantifies that the input alignment swaps from very stable to unstable between both strands. The difference in minimum free energy, on the other hand, is able to specify small changes in energies, which is needed to find the correct reading direction of the ncRNA in case both reading directions result in very stable structures. An example are miRNAs, which are very stable on both strands but are nevertheless successfully classified by RNAstrand. Hence, all four descriptors carry different information.