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Table 3 Formula for calculating retrieval performance parameters for search strategies*

From: Developing search strategies for clinical practice guidelines in SUMSearch and Google Scholar and assessing their retrieval performance

  Manual review
Search terms Meets criteria (unique, relevant CPGs) Does not meet criteria (non-relevant CPGs or duplicates)
Detected a b
Not detected c d
  1. *Following the methodology of the Hedges group (see text): sensitivity = a/(a+c); specificity = d/(b+d); precision = a/(a+b); total sample (all unscreened reviewed retrievals) = a+b+c+d; NNR = 1/precision.
  2. CPG = clinical practice guideline.