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One surprising result was that Query likelihood baselines with smoothing (such as JM, Dir and TS) did not improve the retrieval results over TFIDF for any metrics in TREC CDS and Ohsumed collections as bioCADDIE or previous studies did (http://trec.nist.gov/pubs/trec23/papers/pro-UCLA_MII_clinical.pdf) or. However, type of queries could be an important factor that might cause the differences in retrieval results. This was also mentioned in the study of Zhai C (http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.58.8978) that queries with only keywords tend to perform better than more verbose queries (*** Note: Zhai also mentioned longer queries performed better than short queries)
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