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General representation of diagnostic test.
| Disease status | |||
|---|---|---|---|
| Positive | Negative | Total | |
| Test | |||
| Positive | a | b | a + b |
| Negative | c | d | c + d |
| Total | a + c | b + d | n |
| Test | Disease status | Name | |
|---|---|---|---|
| + | + | True positive (a) | |
| + | − | False positive (b) | |
| − | + | False negative (c) | |
| − | − | True negative (d) | |
Sensitivity = a/(a + c)
Specificity = d/(b + d)
Positive predictive value = a/(a + b)
Negative predictive value = d/(c + d)
Prevalence = (a + c)/n
