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Suppose a team of researchers is interested in conducting a retrospective cohort study to determine if occupational arsenic exposure is a cause of liver cancer among American Adults. The researchers are concerned that geographic location (e.g., Northeast, Southwest, Midwest) may be a confounder of the effect of occupational arsenic exposure on liver cancer. The researchers decide to use restriction to minimize confounding by geographic location. Please describe the following: How restriction can be applied in the context of this study (3 points). How restriction minimizes confounding by geographic location in the context of this study (3 points). 

A team of researchers conducted a prospective cohort study to determine if children who were exposed to secondhand smoke at home are more likely to develop asthma compared to children who were not exposed to secondhand smoke at home. The researchers computed a risk ratio of 1.72 and a standard error of 0.17. As a next step the researchers want to estimate a 95% confidence interval for the risk ratio using the following formula: What value should the researchers use in place of  in the formula?

Smoking during pregnancy is often mentioned as a cause of birth defects, such as cleft lip. However, not all babies born to mothers who smoked during pregnancy develop cleft lip. Use the sufficient cause framework to explain why not all babies born to mothers who smoked during pregnancy develop cleft lip (max. 6 points). Make sure to include the terms component cause and sufficient cause in your answer (max. 6 points). 

Based on the information in Table 1, report the following information: Was it appropriate to estimate an odds ratio using Mantel-Haenszel methods (yes/no)? (2 points) Explain why this is/is not appropriate (2 points). Was it appropriate to estimate a risk difference using Mantel-Haenszel methods (yes/no)? (2 points) Explain why this is/is not appropriate (2 points).

A researcher plans on conducting a prospective cohort study on the association between smoking and respiratory infections among Floridian adults. The researcher thinks that age may be a confounder of the association between smoking and respiratory infections. To minimize confounding by age, the researcher decides to sample the participants in such a way that for every participant who smokes at study entry, they sample a participant of the same age who does not smoke. Which method did the researcher apply to minimize confounding?

Suppose that the true risk difference for the association between childhood adverse events and substance abuse is 0.03 (i.e., individuals who experienced childhood adverse events have a 0.03 higher risk of abusing substances compared to individuals who did not experience childhood adverse events). Suppose that a researcher conducted a prospective cohort study and estimated a risk difference of 0.10 for the association between childhood adverse events and substance abuse (i.e., individuals who experienced childhood adverse events have a 0.10 higher risk of abusing substances compared to individuals who did not experience childhood adverse events). What type of bias is this? 

Which statement is true about a confounder? 

Suppose a team of researchers conducts a randomized controlled trial in which they randomly assigned individuals to either a Mediterranean diet or no diet. After a year they assessed the fasting blood glucose levels of all individuals. Suppose that the mean difference in the fasting blood glucose levels was -22 milligram/deciliter, indicating that individuals with the Mediterranean diet had a lower blood glucose level than individuals who did not follow a specific diet. Also suppose that the p-value for the null hypothesis significance test was 0.01. Is there a statistically significant difference at alpha 0.05 in the fasting blood glucose levels between the two compared groups (yes/no)? (2 points) Explain why you think that there is/is not a statistically significant difference at alpha 0.05 (2 points). 

The fellow researcher is also worried that there may be reverse causation in the study proposed by the team of researchers in case 2. Explain in the context of case 2 what reverse causality means (max. 5 points). 

BONUS (+2)- Define the following blood disorder: pernicious anemia