| Number of Documents |
Relevant
(Rel) |
Not Relevant
(Nrel) |
Total |
| Retrieved
(Ret) |
(RetRel) | (RetNrel) | (RetRel) + (RetNrel) [All Docs Retrieved] |
| Not Retrieved
(Nret) |
(NretRel) | (NretNrel) | (NretRel) + (NretNrel) [All Docs. NOT Retrieved] |
| Total | (RetRel) + (NretRel) [All Relevant Docs] |
(RetNrel) + (NretNrel) [All NOT Relevant Docs] |
(RetRel) + (RetNrel) + (NretRel) +
(NretNrel) [All Docs] |
Recall measures the ability of the user/system to retrieve the available relevant documents.
recall = (RetRel) / ((RetRel) + (NretRel)) = (RetRel) / [All Relevant Docs]
Precision measures the ability of the user/system to retrieve only relevant documents.
precision = (RetRel) / ((RetRel) + (RetNrel)) = (RetRel)
/ [All Docs Retrieved]
Fallout measures the probability that an irrelevant document was retrieved.
fallout = (RetNrel) / ((RetNrel) + (NretNrel)) = (RetNrel) / [All NOT Relevant Docs]
Generality is the proportion of the documents in the system that the query addresses.
generality = (RetRel) + (NretRel) / ((RetRel) + (RetNrel) + (NretRel) + (NretNrel)) = [All Relevant Docs] / [All Docs]
Noise is the proportion of irrelevant documents found in the set of retrieved documents.
noise = (RetNrel) / ((RetRel) + (RetNrel)) =(RetNrel) / [All Docs Retrieved]
Notes:
1. This page adapted from: Pollit, A. S. (1989) Information storage and retrieval systems: origin, development and applications. Toronto: John Wiley & Sons, pp. 164-65.
2. Pollit, A. S. Op. cite. p.164.
3. Lancaster, F.W. (1979) Information retrieval systems: characteristics, testing and evaluation. New York: John Wiley & Sons. Quoted in Pollit, A. S. (1989)Information storage and retrieval systems: origin, development and applications. Toronto: John Wiley & Sons, p.164.