Assignment_IR_2

Assignment_IR_2 - Shakya Deb Ganguly, MSc. 'for attention...

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Unformatted text preview: Shakya Deb Ganguly, MSc. 'for attention of Frost, Dr. Jamie.' GR-1. Question 1. Solution: 1 a) In a Boolean retrieval system, stemming lowers the precision as with stemming the, P (retrieved) increases and hence, the precision (i.e. P (relevant|retrieved)) decreases. Precision P (relevant|retrieved) = ( P (relevant) P (retrieved) ) / P (retrieved) 1 b) In a Boolean retrieval system, stemming never lowers the recall as with stemming the, P (retrieved) increases or remains unchanged and hence, the precision (i.e. P (relevant| retrieved)) increases or remains unchanged. Recall P (relevant|retrieved) = ( P (relevant) P (retrieved) ) / P (relevant) Question 2. Solution: 2 a) Position indices of fools: <2, 4: <1, 17, 74, 222>; // the word has appeared in Document 2, 4 times and in positions 1, 17, 74 and 222. <4, 4: <8, 78, 108, 458>; AND <7, 4: <3, 13, 23, 193>; in: <2, 5: <3, 37, 76, 444, 851>; <4, 5: <10,20,110,470,500>; <7, 4:<5,15,25,195>; rush: <2, 5:<2,66,194,321,702>; <4, 5: <9,69,149,429,569>; <7, 3:< 4,14,404>; So clearly, fools is followed by rush followed by in in all the documents (2,4 and 7). 2 b) angels: <2, 4:< 36,174,252,651>; <4, 4:<12,22,102,432>;< 7,1:<17>; fear: <2, 4: <87,704,722,901>;< 4, 4:13,43,113,433>;< 7, 3: <18,328,528>; to: <2, 4: <47,86,234,999>; <4, 4: <14,24,774,944>; 7, 4: <199,319,599,709>; tread:< 2,3:<57,94,333>; <4,3: <15,35,155>; <7,2: <20,320>; angels fear to tread appears only in document 4. Hence, fools rush in AND angels angels fear to tread appears only in document 4....
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This note was uploaded on 03/28/2012 for the course CS CASL taught by Professor No during the Spring '10 term at Oxford University.

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Assignment_IR_2 - Shakya Deb Ganguly, MSc. 'for attention...

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