In order to achieve more comprehensive results for this evaluation, we implement tests for set variants.
for each set of experiments, we make comparisons not only between the two background corpora being evaluated, but also between each corpus and the union of both corpora; for example for COCA vs. COHA, we not only implement the comparison between COCA and COHA, but also between COCA and COCA + COHA and between COHA and COCA + COHA, where COCA + COHA is the union of COCA and COHA.