Bias Flashcards
Lead time bias?
Early detection confused with increased survival–natural hx of dz is not changed, but early detection makes it seems as though survival increased
“A new improved screening test…”
Lead time bias
Selection bias?
Nonrandom assignment to participation in a study group
Berkson’s bias?
Selection bias–selecting hospital pts as control group
Loss to follow up?
Selection bias
Recall bias?
Knowledge of presence of disorder alters recall by subjects
What studies is recall bias common in?
Retrospective
Sampling bias?
Subjects are not representative of general population; therefore, results are not generalizable (type of selection bias)
Late look bias?
Info gathered at an inappropriate time–e.g. using a survey to study a fatal dz (only those pts still alive will be able to answer survey)
Procedure bias?
Subjects in different groups are not treated the same–e.g. more attention is paid to tx group, stimulating greater adherence
Confounding bias?
Occurs when factor is related to both exposure and outcome, but is not on the causal pathway
Hawthorne effect?
When group being studied changes its behavior owing to the knowledge of being studied
Pygmalion (observer expectancy) effect?
Researcher’s belief in efficacy of tx that can potentially affect the outcome (subjects perform better in response to the expectation placed upon them); prevented by blinding
Social desirability bias?
Pt says what they think is socially desirable rather than saying the truth–e.g. overestimating exercise, under-representing alcohol consumption
How to control confounding?
Matching variables that could be confounders (age, race, etc.)
