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Unit 10: Information Storage and Retrieval System
Notes
Figure 10.3
B: Number of relevant
records not retrieved.
B A A: Number of relevant
records retrieved.
Recall: A × 100%
A+B
PRECISION is the ratio of the number of relevant records retrieved to the total number of irrelevant
and relevant records retrieved. It is usually expressed as a percentage.
Figure 10.4
C: Number of relevant
records retrieved.
A
C A: Number of relevant
records retrieved.
Precision: A × 100%
A+C
Recall and precision are inversely related:
Figure 10.5
100%
As recall precision
Recall
conversely:
As recall precision
0%
0% Precision 100%
In the graph above, the two lines may represent the performance of different search systems. While
the exact slope of the curve may vary between systems, the general inverse relationship between
recall and precision remains.
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