Tuesday, August 30, 2011


Precision and Recall are measures to evaluate the effectiveness of an Information Retrieval System.

Precision = tp/(tp+fp)

Recall = tp/(tp+fn)

tp- Relevant documents retrieved by the system

fp- All documents retrieved by the system, based on the user query

fn – All the relevant documents present

Precision/recall values can be plotted and the area under the Precision/recall curve is a measure of the effectiveness.
Practically, 100% effectiveness is almost impossible to achieve. Why? Because, it is entirely dependent on the User.