Epidemiology - Bias

"Define and specifically discuss the different types of bias within the context of scientific research and their possible consequences in the nutrition field"

Wiki: In science and engineering, bias is a systematic error.  Statistical bias results from an unfair sampling of a population, or from an estimation process that does not give accurate results on average.

Pre-trial bias = Flawed study design, Selection bias, channelling bias
Bias during trial = Interviewer bias, Recall bias, transfer bias, misclassification of exposure or outcome, performance bias, chronology bias
Bias after trial = Citation bias, confounding


How to avoid bias:
Pre-trail bias

Flawed study designs - clearly define risk and outcome. Standardize and blind data collection.

Selection bias - Select patients using rigorous criteria to avoid confounding results. Chose patients from the same population. Avoid selection bias as outcome is unknown at time of enrolment.

Channeling bias - Assign patients to study cohorts using rigorous criteria

Bias during trial

Interviewer bias - Blind interviewer to exposure status and other factors. Standarize interviewers interaction with patient.
Chronology bias - Avoid using historic controls.