Bias - selection Flashcards
Selection bias
Study population does not represent the target population
Berkson bias
Admission rate bias
Neyman bias
Incidence-prevalence bias
When ascertaining causation, one must look for an association between a risk factor between incidence and not prevalence
Response bias
When persons who respond to an invitation to participate in a study are different to those who do not respond
Unmasking bias
When a risk factor unmasks (rather than causes) an event which it is expected to cause
Lead-time bias
Lead-time = The difference in time between the date of diagnosis with and without screening
Need to account for this when looking at survival time
Referral bias
The variation in concentration of rare exposures or diseases between patients in primary and secondary care
Diagnostic purity bias
Exclusion of comorbidities resulting in a non-representative sample, especially problematic in RCTs
Membership bias
Case identification using members of patient’s organisations leading to systematic differences and non-representativeness
