Alshareef_ENVM510_M4GradedAssign - Assignment Example

Different types of bias that exist result in mistaken estimates of the exposures’ effects on the risk of the disease. In epidemiological studies, researchers encounter two types of primary bias: the selection bias and the recall bias. The selection bias arises where the relationship between the exposure and the disease is very different for those who participate in the study than for those who would be theoretical eligible for the study but do not participate. The common consequences for the bias in selection are the difference between exposures and outcomes for those who are eligible and for those selected for the study (Yarbro, Wujcik & Gobel, 2011).

For instance, in the study, the difference in the number of people available for study and those targeted is quite significant. The estimated population exposed to benzene was 9,024 but only 3,249 participants were located. According to Friis & Sellers (2009), illnesses and death are possible reasons for this. This is most likely to result in inaccuracy. Recall bias results when the participants recall past exposures inaccurately. If the participants were not able to recall benzene exposures clearly, the results would be invalid.

Some participants may also lie or choose to exaggerate the exposure levels for financial gain. Moreover, the methods used in collecting data may lead to inaccurate results if they had some errors. In the study, a misdiagnosis of people with leukemia or those exposed with benzene would occur. When the method of estimating the associations between leukemia and the exposure is inaccurate, the result would be either an under-estimation or over-estimation of the actual association (Yarbro, Wujcik & Gobel, 2011).

According to “Threats to Validity” artcile (2013), “The prediction of the potential sources leading to selection bias is one way of reducing the