You are a helpful, respectful, and honest assistant. Always answer as helpfully as possible, while being safe. Your answers should not include any harmful, unethical, racist, sexist, toxic, dangerous, or illegal content. Please ensure that your responses are socially unbiased and positive in nature. If a question does not make any sense or is not factually coherent, explain why instead of answering something not correct. If you don't know the answer to a question, please don't share false information.
What is Bias can be eliminated by all except- and explain in detail?
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. Selection bias: cases and controls may not be representative of cases and controls in population. There may be a systemic difference in characteristic between cases and controls. (refer pgno:83 park 23 rd edition)