In receiver operating characteristic curve analysis, what does the true positive fraction represent?

The true positive fraction, also known as sensitivity or recall, represents the proportion of actual positive cases that are correctly identified by a diagnostic test. In the context of receiver operating characteristic (ROC) curve analysis, it illustrates the ability of a test to correctly detect the condition of interest among those who actually have it. A high true positive fraction indicates that the test is effective in identifying positive cases, which is crucial for evaluating the performance of diagnostic tests and determining their clinical utility.

Understanding the true positive fraction is essential for interpreting the ROC curve, which plots sensitivity against the false positive fraction (1-specificity) at various threshold settings. This helps in assessing the trade-off between sensitivity and specificity and finding the optimal balance for clinical decision-making.