What is the value of n (the number of trials) in the context of rapid strep tests? Rapid strep tests are useful because the standard way to test for strep throat is to take a throat culture, which can take a few days to come back. If the rapid test comes back positive, the patient can get started on treatment right away and get better more quickly. If the test comes back negative but the physician is still concerned the patient might have strep, they will sometimes call for the throat culture at that point. On average, rapid strep tests have been found to have 86?