Topic outline

  • Bias in Clinical Trials

    Collapse all Expand all
    Performing a clinical trial is a very complex and challenging activity. Bias may come in at different levels before, during and after the trial. Therefore, it is important for researchers to be able to interpret the trial results and to be able to identify potential bias in the design, conduct and analysis of a trial which could invalidate the trial analysis and ultimately the validity of the clinical trial itself.

    In research, bias occurs when systematic error is introduced into data sampling or hypothesis testing by selecting or encouraging one outcome or answer over others. Of note, bias is not always introduced intentionally. It can also be caused unintentionally: for example by calibration error or unknown confounding variables. Bias may affect the results of a clinical trial by causing a deviation between the observed effect and its true value: estimates of association can be systematically larger or smaller than the true association. Bias may also take the form of systematic favouritism in the way results are reported or in the way they are interpreted in the discussion and conclusion on clinical trial results.