Table 6 Comparing average P@X of CRFref and the rankers constructed by integrating the baselines with CRFref: All baselines were improved by integrating them with CRFref, however when compared with CRFref, some of the integrated versions achieved better performance in P@3 but not P@1

CRFref

CRFref

0.34435

0.30040

0.28078

CRFref & individual baselines

CRFref + PosFreq

0.33065

0.30202

0.28965

CRFref + PRE

0.32581^s

0.30161

0.28777

CRFref + BM25

0.33548

0.30323

0.28938^s

CRFref + PLM

0.33548

0.30242

0.28589

CRFref + Lucene

0.33306

0.29516

0.28132

CRFref & integrative baselines

CRFref + PRE + PosFreq

0.32258^s

0.30685

0.29073^s

CRFref + BM25 + PosFreq

0.33629

0.30887

0.29019

CRFref + PLM + PosFreq

0.32500^s

0.30524

0.29341^s

CRFref + Lucene + PosFreq

0.33468

0.30161

0.28159