Adapted from Wiki: Positive Predictive Value

Condition
(pre-determined)
Condition Positive Condition Negative
Test
Outcome
Test
Outcome
Positive
True Positive False Positive
(Type I error)
Positive predictive value =
Σ True Positive
Σ Test Outcome Positive
Test
Outcome
Negative
False Negative
(Type II error)
True Negative Negative predictive value =
Σ True Negative
Σ Test Outcome Negative
Sensitivity =
Σ True Positive
Σ Condition Positive
Specificity =
Σ True Negative
Σ Condition Negative

 

 

 

 

 

 

 

 

 
Patients with concussion
Condition Positive Condition Negative
ImPACT
Test
Outcome
Test
Outcome
Positive
True Positive
(TP) = 59
False Positive
(FP) = 7
Positive predictive value
= TP / (TP + FP)
= 59 / (59 + 7)
= 89.4%
Test
Outcome
Negative
False Negative
(FN) = 13
True Negative
(TN) = 59
Negative predictive value
= TN / (FN + TN)
= 59 / (13 + 59)
= 81.9%
Sensitivity
= TP / (TP + FN)
= 59 / (59 + 13)
= 81.9%
Specificity
= TN / (FP + TN)
= 59 / (7 + 59)
= 89.4%