Sensitivity1.0
0.8
0.6
0.4
0.2
0.0
0.0 0.2 0.4 0.6 0.8 1.0
1 – specificity
- The ROC curve obtained for the model fitted to these
data is shown below.
a. Verify that the plots you produced to answer question
2 correspond to the appropriate points on the ROC
curve shown here.
b. Based on the output provided, what is the area
under the ROC curve? How would you grade this
area in terms of the discriminatory power of the
model being fitted?
c. In the output provided under the heading “Associa-
tion of Predicted Probabilities and Observed
Responses,” the number of pairs is 19,950. How is
this number computed?
d. Using the information given by the number of pairs,
the Percent Concordant, and the Percent Tied in the
output under the heading “Association of Predicted
Probabilities and Observed Responses,” compute
the area under the ROC curve (AUC), and verify
that it is equal to your answer to part 3b.
- Consider the following figure that superimposes the
ROC curve within the rectangular area whose height
is equal to the number of MRSA cases (114) and whose
width is equal to the number of MRSA noncases (175).
Test 383
