Part 2: For each of the following scenarios answer the questions about bias that follow. Use complete sentences 1. Smoking and Chronic bronchitis A study to assess the association of chronic bronchitis and smoking compared a group of hospitalized individuals with chronic bronchitis (cases) with a group of volunteer individuals without chronic bronchitis (controls) who were full-time employees of the same hospital where the cases were identified. The results from this study reported, for the rst time in the literature, a strong association between chronic bronchitis and smoking. A. What type of bias may be present? Why do you suspect the presence of the bias you have identified? B. The magnitude of this association is likely to be either over- or underestimated. Which do you think is the case, and what makes you think so? 2. Childhood dental x-rays and thyroid cancer A casecontrol study was conducted to assess the association of childhood dental xrays and thyroid cancer. Newly diagnosed individuals with thyroid cancer (cases) were compared with a random sample of individuals without thyroid cancer (controls) in regard to dental x-rays as a child. A. Which type and mode of bias could be introduced into this study? B. Why do you suspect the presence of the bias you have identified? 3. Airplane travel and Skin Cancer An investigator would like to assess the association of melanoma (skin cancer) and exposure to airplane travel by using a hospital-based casecontrol study. Hospitalized individuals with melanoma will be compared with hospitalized patients without melanoma (controls). This hospital, located in a low-income area of the city, is famous nationwide for its expertise in melanoma. Individuals with melanoma (cases) from all over the country go to that hospital to get the highest quality care that can be provided. However, this hospital is not as well known for any other medical conditions as it is for melanoma. Therefore, cases would come from all over the country, and controls will be mostly local low-income individuals. The investigator predicts that an overestimation of the association between melanoma and airplane travel may occur. A. Do you agree or disagree with the investigator? Explain your answer in a few sentences. B. Please explain what type of bias may be present