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Receiver Operating Characteristics (ROC) curve
What is an ROC curve? ROC curves are made to help decide on a good cutoff point for a test. If the cutoff is very high, there will be too many false negatives but few false positives. Whereas, if the cutoff is too low there will be too many false positives and few false negatives. To do this, the true positive rate (sensitivity) and false positive rate (1 – specificity) of the test are calculated for several possible cutoff points. Then these are plotted to create the ROC curve and the area under the curve can be measured to determine the overall accuracy of a test. Notice that the ROC…
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Biostatistics Questions
A new blood test to detect prostate cancer is evaluated in 300 male volunteers. A needle biopsy of the prostate gland is done on all men with serum prostate-specific antigen concentrations greater than 5 ng/mL (N<4). One hundred men undergo biopsy procedures; 90 are found to have prostate cancer, and five are found to have chronic prostatitis. Which of the following is necessary to calculate the sensitivity of this test? (A) Incidence of chronic prostatitis in the general population (B) Number of men with test results greater than 5 ng/mL and a normal biopsy specimen (C) Prevalence of chronic prostatitis in the general population (D) Prostate biopsies of men with…
