One found set, two different denominators
A conceptual set diagram; regions are not drawn to scale
ALL RELEVANT RECORDS
Returned, not relevant
Relevant and returned
Relevant, not returned
Extra material
Found support
Missing support
ALL RETURNED RECORDS
Precision asks
Of what came back, how much was relevant?
Recall asks
Of what was relevant, how much came back?
Neither measure checks whether the answer represents sources accurately.
Conceptual illustration • not measured data