| Summary: | 碩士 === 國立臺北大學 === 統計學系 === 100 === The accuracy of a binary diagnostic test can be assessed easily through
comparing the results with the status of respondents. That is, the sensitivity
and specificity are evaluated. However, when the diagnostic test is resulted in
a continuous version, the accuracy depends upon the specified threshold. The
ROC curve (receiver operating characteristic curve) that includes all possible
combinations of sensitivity and specificity, provides a way to evaluate an
overall evaluation of the diagnostic test. Nevertheless, in practice, a threshold
is still needed to have an easier clinical representation. The determination of
a proper threshold depends upon the definition of accuracy.
The determination of the accuracy depends on how important the prac-
titioner views the specificity and sensitivity. Given a particular concern of
specificity and sensitivity, this thesis derives the optimal threshold under
two commonly used parametric assumptions on the diagnostic test (Binor-
mal model and Bilogistic model). Since the optimal threshold does not have
a closed form, the numerical results are given in tables for many parameter
settings, so the practitioner can easily find the optimal threshold for their
studies.
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