Epidemiology Assignment Solution: Analysis of Study Designs and Biases

This report provides a detailed analysis of an epidemiology assignment, focusing on case-control and cohort study designs. It examines the purpose of control groups, advantages and disadvantages of case-control studies, and the importance of controlling for confounding factors. The solution addresses recall and selection bias, highlighting how they can affect study results. Furthermore, it explores the differences between case-control and retrospective cohort studies. The assignment also discusses the criteria for a confounding factor, providing a comprehensive overview of epidemiological concepts. References are provided to support the analysis.

Running head: EPIDEMIOLOGY
Epidemiology
Name of the Student
Name of the University
Author note

1EPIDEMIOLOGY
Answer to question 2
a) The purpose of the control group in the case control design is determination of the
relative size of the unexposed an exposed categories of the source population (Breslow, 2014).
b) It is advantageous as it reduces the selection bias and recall bias when recruiting
women with women breast cancer. When asked about the previous exposure both case and
control may give same quality of information.
The disadvantage includes difficulty calculating the incidence or absolute risk and there
may be distortion of the relative risk. It may happen because the pattern of referral of cases in
the hospital based case control study may differ with those of control diseases who are not
representative of the source population (Breslow, 2014).
c) The reason for this decision in the study is to eliminate the confounding. It will help
gain the efficiency (Pourhoseingholi et al., 2012).
Answer to question 5
The case control study determines the possible exposure factors after the incidence of the
known disease. On the contrary the retrospective cohort study the risk of developing a given
disease (breast cancer) is compared to the known exposure factors (Panageas et al., 2018).
Answer to question 6
a) It is the example of the recall bias as there maybe differences in the accuracy of the
recollections by participants regarding the past experiences of Parkinson’s disease and head
injuries (Song & Chung, 2010).

2EPIDEMIOLOGY
b) It is known as selection bias as the participants are selected in manner that proper
randomisation is not obtained because the sample is not objectively represented.
c) The three criteria for sex to be considered as the confounder for the risk factor and the
outcome are-
 Difference in ethnicity of the same sex people
 Genetic influence may alter the disease between same sex
 Ancestry such as place of birth or grandparents (Westfall & Yarkoni, 2016)

3EPIDEMIOLOGY
References
Breslow, N. E. (2014). Case-control studies. In Handbook of epidemiology (pp. 293-323).
Springer New York.
Panageas, K. S., Goldman, D. A., & Kingham, T. P. (2018). Design of Retrospective and Case-
Control Studies in Oncology. In Methods and Biostatistics in Oncology (pp. 147-164).
Springer, Cham.
Pourhoseingholi, M. A., Baghestani, A. R., & Vahedi, M. (2012). How to control confounding
effects by statistical analysis. Gastroenterology and Hepatology from bed to bench, 5(2),
79.
Song, J. W., & Chung, K. C. (2010). Observational studies: cohort and case-control
studies. Plastic and reconstructive surgery, 126(6), 2234.
Westfall, J., & Yarkoni, T. (2016). Statistically controlling for confounding constructs is harder
than you think. PloS one, 11(3), e0152719.