The estimation method starts with a training file which indicates, among other things, the number of relevant and irrelevant documents for each term t in each training query, q.
for each t and q, we are are given dr (t, rel, tfo) and dr (t, tel, tfo), where dr(t, tel, tfo) is the number of relevant documents d with tf(t, d) = tfo, and df (t, rel, tfo) is the number of irrelevant documents d with tf(t, d) = tfo.