In a four‐week period, 28 patients arrive at an emergency department with chest pain. Each has their serum CK‐BB (μg/l) level measured as a diagnostic test for a possible AMI. Twenty of these individuals are in fact experiencing an AMI but eight are not (although the clinicians do not know who is and who is not). As an indicator of probable AMI, the clinicians decide to use as a cut‐off, a particular value of serum CK‐BB. Above this cut‐off, the individual concerned is judged likely to be experiencing an AMI and will be treated accordingly, and below this value, they are not. The levels of serum CK‐BB among the 28 individuals are shown in Figure 27.2. What is the sensitivity and specificity of the test, if the cut‐off value is
(a) 12μg/l and
(b) 8μg/l?
