Q1. a) A study found an association (relative risk) between condom use and sexually transmitted infection of 0.28. After adjusting for age, the relative risk was 0.54. This suggests:

• Age was not a confounder
• Age was a positive confounder
• Age was a negative confounder

b)In a case-control study, unadjusted odds of previous transplant among sepsis cases was 2.2 times that of controls. After adjusting for gender, the odds ratio was 3.1. This suggests:

• Gender was not a confounder
• Gender was a positive confounder
• Gender was a negative confounder

c)In a study on vegetable consumption and bone density, we find that gender is associated with bone density, but not with vegetable consumption. Additionally, the association between vegetable consumption and bone density is similar across genders. Gender is most likely to be:

• A confounder
• An effect modifier
• Both a confounder and an effect modifier
• Neither a confounder nor an effect modifier

d)In a study on laptop use and vision deterioration, we find that younger participants are more likely to use laptops and less likely to experience vision deterioration independent of laptop use. Additionally, the association between laptop use and vision deterioration is similar across all age groups. Age is most likely to be:

• A confounder
• An effect modifier
• Both a confounder and an effect modifier
• Neither a confounder nor an effect modifier

e) In a study on the effectiveness of a novel vaccine protecting against malaria, you restrict your sample to a specific high-risk region. This ensures:

• Region is not a confounder
• Region is not an effect modifier
• Region is neither a confounder nor an effect modifier
• None of the above