This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Social & Preventive Medicine
[{'content': 'Likelihood ratio for positive results is; \nSelect and explain. \nA. Sensitivity / (1-specificity), B. Specificity / (1-Sensitivity), C. (1-Sensitivity) / Specificity, D. (1-specificity) / Sensitivity', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Likelihood ratio for Positive :\n\xa0 \xa0 \xa0 \xa0LR+=\xa0Sensitivity / (1-specificity)\nLikelihood Ratio for Negative :\n\xa0 \xa0 \xa0 LR-\xa0=\xa0(1-Sensitivity) / Specificity', 'role': 'assistant'}]