1 The association between cellular telephone use and the risk of brain cancer was investigated in a case-control study. The study included 475 cases and 400 controls and the following results were seen: Cellular Phone User Yes No Total Cases 270 205 475 Controls 200 200 400 Calculate the odds ratio based on these data. The p value for this odds ratio is 0.06. State your interpretation of this p-value. Gender was considered a potential confounder and effect measure modifier in this study. The data were stratified into males and females in order to assess these issues. Cellular Phone User 1. 1. Yes No Males Cases 242 100 Controls 150 50 Yes No Females Cases 28 105 Controls 50 150 Calculate the stratum-specific odds ratios. Is gender a confounder in this study? Briefly justify your answer. Is gender an effect measure modifier in this study? Briefly justify your answer. QUESTION 2 A study used self-administered mail questionnaires to gather data on height and weight in order to calculate a measure of obesity. Which of the following types of problems were likely avoided by this method of data collection, and why? Interviewer bias Exposure misclassification Confounding Selection bias Loss-to-follow-up QUESTION 3 A case-control study was performed to determine whether head injury was associated with an increased risk of brain tumors in children. 200 cases with brain cancer were identified from the state cancer registry and 200 controls were recruited from 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 the 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