1. Below are statements that describe necessary and sufficient causes. Write the letters corresponding to the characteristics under the right category in the table below.

a. Multiple component causes act together to produce disease

b. HIV significantly weakens the immune system before AIDS develops

c. Among cancer patients, some developed the disease after smoking for years but other study participants who did not smoke had a family history of cancer instead

d. Educating people about healthy diets and regular exercise prevents cardiovascular disease

e. In the absence of SARS-CoV-2, people will not develop COVID-19

f. The minimum set of risk factors and circumstances that will produce the disease

Necessary Cause	Sufficient Cause
[ Select ] ["a", "b", "c", "d", "e", "f"]	[ Select ] ["a", "b", "c", "d", "e", "f"]
[ Select ] ["a", "b", "c", "d", "e", "f"]	[ Select ] ["a", "b", "c", "d", "e", "f"]
[ Select ] ["a", "b", "c", "d", "e", "f", ""]	[ Select ] ["a", "b", "c", "d", "e", "f", ""]
[ Select ] ["a", "b", "c", "d", "e", "f", ""]	[ Select ] ["a", "b", "c", "d", "e", "f", ""]

Part II: Validity, Bias, Confounding

2. A case-control study of the relationship between coffee drinking and osteoporosis found that osteoporotic women were 2 times as likely to drink coffee than those who did not have osteoporosis. Upon further analysis, the investigators found that the age distribution was different in the two groups: cases (osteoporotic women) were on average 25 years older than the women who did not have osteoporosis. They reported the results at a big conference. What would you say to the investigators?

Group of answer choices

a. The results of your study are not valid because age is a confounder and will distort your results

b. The results of your study are valid because the different age distribution is due to random error

c. The results of your study are not valid because the different age distribution will bias the results

d. The results of your study are not valid because they cannot be generalized to the whole population

3. One statement about confounding below is not true. Which one?

Group of answer choices

a. The effect of a third factor distorts the association between exposure and outcome.

b. The statistical dependence between the exposure and the disease is referred as association

c. A "cause" is an event, condition, characteristic (or combination) that affects the outcome

d. A factor cannot be a confounder if it is associated with both the exposure and the disease

4. The three major classes of bias in epidemiologic studies are:

Group of answer choices

a. Random error, confounding, selection bias

b. Confounding, selection bias, information bias

c. Information bias, reporting bias, chance

d. Random error, validity, confounding

5. You attend a research presentation on food fortification with folic acid for the prevention of spina bifida and anencephaly. Taking folic acid during pregnancy prevents major birth defects of the baby's brain and spine (i.e., spina bifida and anencephaly). You suspect that the researchers probed mothers of children with spina bifida with several questions about their consumption of foods fortified with folic acid but not the controls. This is an example of:

Group of answer choices

a. Selection bias

b. Interview bias

c. Observer bias

d. Recall bias

6. Briefly explain why you picked this answer.