Bias may occur at different points in a study and is often difficult to measure. All of the following methods are used to eliminate bias in studies, EXCEPT:

Bias: Bias is a systematic error that occurs in a study and leads to a distoed result. Methods used to eliminate bias: Randomization Blinding Matching Concealed allocation Uniform follow-up Accurate accounting of co interventions Full disclosure of the fate of all patients Also know: The most common classification divides bias into three categories: Selection bias occurs when factors that lead to selection of the study population affect the likelihood of the outcomes or exposures evaluated. Information bias occurs when the assessment of exposure or outcome may differ between the groups being compared. Confounding refers to the mixing of the effect of an extraneous variable with the effects of the exposure and disease of interest. Ref: Paikin J., Crowther M.A. (2012). Chapter 70. The Quality of Evidence. In G.V. Lawry, S.C. McKean, J. Matloff, J.J. Ross, D.D. Dressler, D.J. Brotman, J.S. Ginsberg (Eds), Principles and Practice of Hospital Medicine.