a false association that results from to the failure to account for some skewing or influencing factor, or a tendency for the observed results to deviate from the "true" results. Bias distorts results in a particular direction. For example, if an investigator in a clinical trial believes the drug under study to be effective and knows which participants are receiving the drug, bias may influence his/her observations in favor of positive results.
BIAS
Meaning of BIAS in English
AIDS English Glossary. Английский словарь СПИДа. 2012