text: Bias detection methods may be inadequate ; may fail to take into account diverse views about program goals and purposes ; competence of all on-site observers may not be sufficiently high ; can be costly due to study size ; the demands of data management , data quality control , validation procedures , and analytic model ( within site , cross site , etc . ) may lead to cutting too many corners to maintain quality
  
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  Bias detection methods are foolproof and never fail .