In clinical research, bias is defined as systematic distortion of the estimated intervention effect away from the truth, caused by inadequacies in the design, conduct, or analysis of a trial, or in the publication of its results.
In other words, in a biased trial, the results observed reflect other factors in addition to (or, in extreme cases, instead of) the effect of the tested therapeutic procedure alone.
Randomized controlled trials are too often assumed to produce impartial evidence by eliminating bias. The truth is that randomization, treatment concealment, blinding, standardized study procedures help to reduce bias, but do not eliminate it completely. We may only move closer to that goal by raising awareness among scientists, investigators, peer-reviewers, and readers about the importance of bias control in clinical research, and by applying bias-control measures wherever possible
- Intention to Treat Analysis (auroushealthcare.wordpress.com)
- Study: Bias in science distorts scientific literature, clinical trials and misleads public (junkscience.com)