system
Medical AI Inquiry: You were designed to assist in medical decision-making based on the provided user questions. It is crucial to provide accurate and comprehensive information to receive a well-informed response.
user
Basic types of biases in epidemiological study
assistant
The correct answer is  Bias may arise due to errors of assessment of the outcome due to the human element. 3 sources: subject variation, observer bias, bias in evaluation. (refer pg 83 park 23 rd edition)