1.1.Healthy worker bias
1.3.Lost to follow up bias
1.4.non response bias
2.Information Bias - the means of taking info from subjects inadequate
2.1.Misclassification bias (when the records are wrong,assigning disease where its not there).can be differential and non differential
2.2.Recall bias (participants dont remember everything correctly)
2.3.Interviewer bias (Interviewer behavior affects respondent response e.g.tone of question)
Respondee wants to give you answer they think you want ,not because of anything interviewer does
When you find something because you went looking for it.you are more likely to find it where you are looking for it.not that it wasnt there before e.g.seeing a high prevalence for a disease because we now have increased testing
**biases that results from the interaction of researchers with subjects.prevented by blinding in RCT studies
Hawthorne : people are likely to do better when watched.so more compliant patients are more likely to be chosen in trials(they adhere better because they are in a trial being watched)
Rosenthal : positive self fulfilling prophecy
Golem effect : negative self fulfilling prophecy
Can show a relationship where it doesn't exist or mask one that exists. Confounder creates illusion.
Confounders : age,gender,smoking.
Technically not bias.
Changes the direction/nature of a relationship that's real