This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Confounding and Bias, Subject name: Social & Preventive Medicine
[{'content': 'All of the following are investigator bias except:- \nSelect and explain. \nA. Interviewer bias, B. Misclassification bias, C. Hawthorne bias, D. Pygmalion bias', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Bias:- Type of Systemic Error in Study; Subject Bias (Eg : Recall Bias, Hawthorne bias) Investigator Bias (Interviewer Bias, Misclassification Bias, Selection Bias) Analyzer Bias (calculation error)', 'role': 'assistant'}]