Question

This module discussed the importance of selecting a suitable study design and methods for data analysis based on a research question. For each of the following research questions. state the type of study described by each of the following paragraphs. Also explain your reasoning for why you chose the study type.

a. The Tumor Registry in a certain US state was used to identify all primary cases of bladder cancer in the state during a given period. These cases were compared to a sample of non-cases from the same state that have been matched on age and time of diagnosis. All subjects or their surviving relatives in both groups were interviewed to collect information on saccharin consumption and other known risk factors for bladder cancer.
b. In the Hanford study of nuclear power workers (1977), 3500 certified deaths occurred among plant workers between 1944 and 1972. Among these deaths, a significantly greater proportion of workers exposed to low levels of ionizing radiation than unexposed workers had died of RES (reticuloendothelial system) cancers.

Answer 1

The study in question a is a case-control study, chosen due to the comparison of cases with controls matched by certain criteria. The study in question b is a retrospective cohort study as it follows an exposed group over time and compares outcomes. The study in question 8 is also a case-control study as it contrasts individuals with a disease to those without based on prior behavior.

Step-by-step explanation:

For question a, the described study design is a case-control study. In this type of study, participants who have the outcome of interest (in this case, bladder cancer) are known as cases and are compared to participants who do not have the outcome, known as controls. The controls in this situation have been matched for age and time of diagnosis, which helps to reduce confounding variables. This approach is ideal for studying conditions that are relatively rare, like certain types of cancer.

For question b, the study is a retrospective cohort study. This determination is made because it examines a group of workers over time looking back from the endpoint to identify exposures to low levels of ionizing radiation and the resulting health outcomes such as deaths from reticuloendothelial system (RES) cancers.

For questions d and e, the study designs are not explicitly mentioned, but given that they involve selecting individuals for interviews or examination, these could be the beginnings of cross-sectional studies or even preliminary steps in a cohort or case-control study depending on the research parameters set forth after initial selection.

Regarding question 5, this is an experimental study where one group of mice is receiving a treatment (the anti-cancer drug) and another group is not, possibly acting as a control group. The observation of energy levels is a qualitative aspect, while determining the tumor size at the end of the study yields quantitative data.

Lastly, question 8 describes another case-control study as it compares individuals with a disease (in this case, diabetes) to those without the disease, assessing their prior soda consumption behavior.