Selection bias in epidemiological studies
What is selection bias? Systematic error in how subjects are selected or loss to follow-up during the study. Selection bias occurs when we found there is a discrepancy between target population and source population. This bias usually arises during the data collection procedure. In case control study, if selection of control group is not appropriately represented by the source population where case rises than we have selection bias. In cohort study, if the population who are dropped out are showing differential pattern in exposure and disease groups then we can say there is a selection bias. In the experimental trial, loss to follow-up differs from one treatment group to another. Selection bias is more concerning in a case-control study than in a cohort study because the study participants have all the available information from the source population. Example : 1. For example, participants included in an influenza vaccine trial may be healthy young a...