Bias can be eliminated by all except-
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)
Matching
Blinding
Randomization
Multivariate analysis
Epidemiology