Question

How can we reduce bias in collecting data in the research? Support the answer with references

Answer 1

In epidemiological studies, all efforts should be made to avoid biasing the selection of study participants. Selection bias can be reduced by paying attention to the following:

1. The study population should be clearly identified i.e. clear definition of study population.

2. The choice of the right comparison/ reference group (unexposed or controls) is crucial. for example, in an occupational cohort study, rather than comparing workers with the general population (which includes people who are too ill to work), ensure all subjects in the comparison are workers, and avoid bias from the Healthy Worker Effect . Compare workers in a specific job with those in jobs that differ in occupational exposures or hazards e.g.

3. select an external comparison group from another workforce e.g. in a situation where all workers of an occupational cohort had some degree of exposure [2]

   • select an internal comparison group within the same workforce e.g. if some workers had exposure while others did not [2].

4. In a cohort study:

   • exposed and unexposed groups should be identical but for the exposure

   • in a retrospective cohort study, the selection of exposed and unexposed groups should be done without knowing the outcome (disease status).

5. In a case-control study:

   • the control group should reflect the exposure of the population which gave rise to the cases

   • controls should be selected independently of the exposure status

     • for example, non-response bias happens when participation into a study is related to the exposure status

   • precise case definition and exposure definition should be used by all investigators.