Final answer:
The question pertains to the interpretation of a positive tuberculin skin test used to diagnose tuberculosis. A positive test result for healthy individuals with no risk of exposure is an induration of 15 mm or more. Understanding errors in testing, a ß level of 0.20 indicates a 20% chance of failing to detect TB when it is present, while an α level of 0.10 indicates a 10% chance of falsely detecting TB when it is not present.
Step-by-step explanation:
The question is about the tuberculin skin test, also known as the Mantoux test, which is used to diagnose tuberculosis (TB) infection. When a person is given the test, a small amount of tuberculin protein derivative is injected into the skin, and the area is then observed after 48-72 hours. For healthy individuals with no risk of TB exposure, a positive test result is typically indicated by an induration (hard, raised red area) of 15 mm or more. In other populations, such as those with a higher risk of exposure or lower immune function, smaller indurations of 5 mm or 10 mm may be considered a positive result.
It's important to understand the potential for errors in screening tests. The beta level (ß level) refers to the probability of a Type II error, which is failing to detect the disease when it is present. A ß level of 0.20 means there is a 20 percent chance of this type of error occurring in the test. Similarly, the alpha level (α level) refers to the probability of a Type I error, which is incorrectly diagnosing the disease when it is not present. An α level of 0.10 indicates a 10 percent chance of this type of error.