Please answer these questions:
a study used self-administered mail questionnaires to gather data on height and weight in order to calculate the measure of obesity. Which of the following types of problems were SURELY AVOIDED by this method of data collection and why.
1. interviewer bias, 2. exposure misclassification 3. confounding 4. selection bias, 5. loss to follow up
a case-control study was performed to determine whether head injury was associated with an increased risk of brain tumor in children. 200 cases with brain cancer were identified from the state cancer registry and 200 controls were recruited fro the same neighborhoods where the cases lived. the mothers of the children completed a questionnaire that asked them to describe their child’s past history of head injury. the investigators found that the mothers of the children with brain tumors reported a past head injury for 70 of cases while a past history of head injury was reported in 30 of the controls. what type of bias was likely to have influenced the findings of this study and why? what can be done to minimize this type of bias.
Expert Solution Preview
Introduction: The following questions are related to epidemiological studies and data collection methods used in medical research.
1. Which types of problems were surely avoided by using self-administered mail questionnaires to gather data on height and weight for a study on obesity?
The self-administered mail questionnaires method of data collection avoids interviewer bias, exposure misclassification, and selection bias. Interviewer bias can occur in studies where data collectors interview participants and may unintentionally influence their responses or record subjective observations. Exposure misclassification occurs when information about the exposure or disease status is inaccurately recorded, leading to inaccurate results. Selection bias occurs when the sample of participants is not representative of the population, leading to biased results. However, using self-administered mail questionnaires to gather data on height and weight may not prevent loss to follow-up or confounding, which can still occur.
2. What type of bias was likely to have influenced the findings of the case-control study on the association between head injury and brain tumors in children? What can be done to minimize this type of bias?
The type of bias that was likely to have influenced the findings of the case-control study on the association between head injury and brain tumors in children is recall bias. This occurs when the cases and controls differ in their ability to accurately recall past exposures or events, leading to biased results. In this study, the mothers of the children with brain tumors may have over-reported past head injuries because they were aware of the association between head injury and brain tumors. To minimize this type of bias, the study could have used medical records or other objective measures to verify the history of head injury. Additionally, blinding the data collectors to the participant’s case/control status could help reduce bias.