In order to create a set of terms related to a topic of interest, we used the Hyper-geometric (HG) test.
given the number of sentences in the union of articles identified for all topics; the number of sentences in the articles identified for a specific topic, i.e., in the topic articles; the total number of sentences that include a particular term, t; and the number of sentences within the topic articles, that include t, denoted x; we use the HG test to assess the probability p, to observe ≥ x occurrences of t within sentences selected at random out of the total population of sentences.