This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Biostatistics, Subject name: Social & Preventive Medicine
[{'content': 'Standard error of mean is calles as - \nSelect and explain. \nA. Standard detion, B. Mode, C. Median, D. Variable', 'role': 'user'}, {'content': 'Answer: A \nExplanation: <p> Standard detion. Reference:Park&;s textbook of preventive and social medicine,K.Park,23rd edition,page no:850. <\\p>', 'role': 'assistant'}]