SP500215 NIST Special Publication 500-215: The Second Text REtrieval Conference (TREC-2) On Expanding Query Vectors with Lexically Related Words chapter E. Voorhees National Institute of Standards and Technology D. K. Harman :1 C" A unexpanded A expanded 0.0 0.2 0.4 0.6 0.8 1.0 Recall 5 .5 a Figure 3: Effectiveness of expanded versus unexpanded routing queries on test documents (disk 3). ½ A unexpanded A expanded 0.0 0.2 0.4 0.8 0.8 1.0 Racall Figure 4: Effectiveness of expanded versus unexpanded ad hoc queries. 229