Describe the common characteristics and design of a case-control study. Discuss the three
important features when it comes to selecting cases and controls, and identify a situation when
one of these might be violated. Discuss the limitations of using questionnaires for determining
exposure status and provide examples of alternative strategies for collecting this information in a
Case-control studies follow a standard policy and design characterized by factors such as the
identification of individuals exhibiting similar signs and symptoms to a particular illness. A
second group of people (the control group) is obtained from the same population and has the
same size. The information acquired from this source population is further compared with
regards to the exemplification of the symptoms to a particular illness or outcome of interest,
referred to as cases (Jiang & Ding, 2017). Similarly, the comparison against the individuals in
the control group who do not portray the signs or symptoms identified (controls). These are
coupled with the retrospective retracing of how frequent the exposure to the risk factors occurs in
each group, thereby facilitating the determination of its relationship with the disorder. Besides,
case-control studies focus on estimating the odds at which an individual is likely to develop an
illness or experience a particular event.
Jiang & Ding (2017), point out that the salient features in the selection of cases and
controls include identifying and classifying the individuals obtained from the source population
into the exposed and unexposed cohorts. These are followed closely by sampling the control
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group to match the cases in all aspects. However, the inclusion of the exposure status in the
selection and sampling of the control group would culminate in a violation of the cardinal
requirement as it is used in the estimation of the distribution of exposure.
Besides, the limitations associated with the use of questionnaires in determining the
exposure status entail a differential recall bias in the quality of data obtained from the source
population that negatively impacts the study in suggesting an artificial relation. Additionally,
there are challenges in the identification of an appropriate control group as some respondents
have the tendency of providing inconclusive and misleading information regarding their
exposure to a disorder or not (Jiang & Ding, 2017). Conversely, the alternative strategies for
collecting information in a case-control study include the random selection of a sample and
including the participants in a phone survey, thereby eliminating potential differential recall bias.
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Jiang, Z., & Ding, P. (2017). The directions of selection bias. Statistics & Probability
Letters, 125, 104-109.