self administered mail questionnaires to gather data on height and weight health and medical assignment help

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.

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