Software is available to build phylogenetic trees from data sets.
For each collection of four taxa, the best tree for those species alone is computed either by the criterion of Maximum Parsimony or by the criterion of Higher Order Parsimony, which introduces a correction to Maximum Parsimony that reduces the effect of long-branch attraction. If there is a large gap between the treelength of the best tree and the runner-up tree, we have high confidence in the correctness of that tree. Data about all the trees for four species at a time are placed in a list. We seek to find a global tree by combining together the best trees for each group of four taxa, using primarily the trees in which we have high confidence. Optionally, the user may also utilize an error-correction process which modifies the trees previously selected for each quartet so as to increase the degree of consistency among the quartets.