Example 1.

TPR=25%; TNR=50%
Likelihood of disease 40%
Number of patients=10
With disease	4	Without disease	6
True positives	1	True negatives	3
False negatives	3	False positives	3
TPR=TP/with disease=1/4=25%		TNR=TN/without disease=3/6=50%
Likelihood of disease 80%
Number of patients=10
With disease	8	Without disease	2
True positives	2	True negatives	1
False negatives	6	False positives	1
TPR=TP/with disease=2/8=25%		TNR=TN/without disease=1/2=50%
In the example above, the likelihood of disease varies from 40 to 80%. Note that although the number of persons that test positive or negative for disease change in each scenario, the TPR and the TNR remain the same.