Formulae for the calculation of operating characteristics for a search filter for locating studies in MEDLINE
| Relevant articles | Non-relevant articles | Total | |
|---|---|---|---|
| Search term + | a (true positive) | b (false positive) | a+b |
| Search term − | c (false negative) | d (true negative) | c+d |
| Total | a+c | b+d | a+b+c+d |
Comprehensiveness=Sensitivity=Recall=a/(a+c).
Efficiency (=Precision=a/(a+b)), expressed more user-friendly as Number Needed to Read (=1/precision).
Specificity=d/(b+d).
Accuracy=(a+d)/(a+b+c+d).