Q waves on the electrocardiogram, according to Schinkel et al. (A-15), are often considered to be reflective of irreversibly scarred myocardium. These researchers assert, however, that there are some indications that residual viable tissue may be present in Q-wave-infarcted regions. Their study of 150 patients with chronic electrocardiographic Q-wave infarction found 202 dysfunctional Q-wave regions.

With dobutamine stress echocardiography (DSE), they noted that 118 of these 202 regions were viable with information from the DSE testing. Construct a 90 percent confidence interval for the proportion of viable regions that one might expect to find a population of dysfunctional Q-wave regions.