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': 'Random error - \nSelect and explain. \nA. Systemic error, B. Bias, C. Reduces precision, D. Confounding factor', 'role': 'user'}, {'content': "Answer: D \nExplanation: Ans. is 'd' i.e., Reduces precision", 'role': 'assistant'}]