Biochemical markers are used by emergency room physicians to aid in diagnosing patients who have suffered from acute myocardial infarction (AMI), or what's commonly referred to as a heart attack. The gold standard test for AMI checks for the presence of a chemical called troponin I to determine if an AMI occurred. Another test for AMI uses the chemical marker creatine kinase (CK). Below is a table that cross classifies the diagnosis of AMI by the troponin I test and the CK test in a sample of 510 subjects. Troponin | Test (Gold Standard). CK Test AMI No AMI AMI 68 43 No AMI 115 284 What is the estimated specificity of the CK test? O 43 / (43 + 284) O 115 / (68 + 115) 68 / (68 + 43) O 68 / (68 + 115) O 284 / (43 + 284) Screenshot