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': 'Mean Hb values in two population groups are compared by \nSelect and explain. \nA. Paired t test, B. Unpaired t test, C. Chi square test, D. Fischer test', 'role': 'user'}, {'content': "Answer: B \nExplanation: Ref:Park's Textbook of Preventive and Social Medicine 25th Ed", 'role': 'assistant'}]