Specificity
Definition: The ability of a test to correctly identify those who truly did not have disease. This term answers the question, “Does the test exclude subjects without disease?” Specificity is:
Calculating Specificity
Specificity can be calculated using a 2x2 table and the following formula: Specificity = D / (C+D).
| Disease Yes | Disease No | Total |
|
| Detected Yes | True + (A) | False + (B) | A+B |
| Detected No | False – (C) | True – (D) | C+D |
| A+C | B+D | A+B+C+D |
