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': 'The PEFR of a group of 11 year old girls follow a normal distrubution with mean 300 1/min and standard deviation 20 1/min - \nSelect and explain. \nA. About 95% of the girls have PEFR between 260 and 340 1/min., B. The girls have healthy lungs, C. About 5% of girls have PEFR below 260 1/min., D. All the PEFR must be less than 340 1/min.', 'role': 'user'}, {'content': 'Answer: A \nExplanation: 1 SD includes → 68% of values\n2 SD includes → 95% of values\n3 SD includes → 99.7% of values\n\nIn this question\nMean PEFR = 300 L/min\nSD = 2 L/min\n\nArea around 1SD on either side of mean (x ± 1SD) will include 68% of values, i.e.\n\nx± 1SD=300±20\nSo, 68% of girls have PEFR between 280 & 320 L/min.\n\nArea around 2SD on either side of mean (x ± 2SD) will include 95% of values, i.e.\n\nx±2SD=300±40\nSo, 95% of girls have PEFR between 260 & 340 L/min.\n\nArea around 3SD on either side of mean (x ± 3SD) will include 99.7% of values, i.e. -\n\nx ±3SD = 300 ± 60\nSo, 99.7% of girls will have PEFR between 240 & 360 L/min.', 'role': 'assistant'}]