General instructions:
Please complete the following assignment corresponding to Parts 1 & 2 of Bias in Epidemiological Studies by no later than Monday, November 16th at 11pm SAST/12am EAT.
At the end of the assignment we ask you to please note 1) approximately how much time you spent on the homework and how much time you spent reviewing the materials (videos and learning checks) , 2) what questions, if any, you have from the videos and/or any places you might have gotten stuck in the assignment, and 3) provide your feedback on the this week’s content and materials. Thank you once again for your assistance in completing these additional questions!
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Question 1 of 27
1. Question
Consider the following DAG. Using this DAG, answer TRUE or FALSE for Questions 1-7.
1. A and U are associated.
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Question 2 of 27
2. Question
2. U and Z share a common direct cause.
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Question 3 of 27
3. Question
3. There is a backdoor path from Y to Z.
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Question 4 of 27
4. Question
4. Z has an indirect effect on L.
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Question 5 of 27
5. Question
5. The DAG is partly incorrect because there is a feedback loop.
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Question 6 of 27
6. Question
6. Z is a collider on one path from A to U.
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Question 7 of 27
7. Question
7. Y is a common cause of A and L.
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Question 8 of 27
8. Question
8. Imagine that in a large observational study comparing people who regularly take >=400 IU of vitamin D per day with people with no supplemental vitamin D intake, the crude incidence rate ratio of multiple sclerosis was 0.34. Smokers are less likely to take vitamin supplements and they are more likely to develop multiple sclerosis. If the authors of the observational study further adjust for smoking, the resulting adjusted incidence rate ratio may be (select all that apply):
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Question 9 of 27
9. Question
The Dutch famine of 1944–45 was a famine that took place in the German-occupied Netherlands, which created the conditions of a natural experiment. A study published in 1996 (Susser et al, 1996) showed a positive association between prenatal famine and risk of Schizophrenia in the Dutch famine birth cohort. A commentary on this paper was published the next year (Van Os, 1997), arguing that the positive association reported by Susser et al was confounded by social class. (Reading the articles may help but is not necessary).
9. Draw a DAG to demonstrate how lower social class may confound the association between prenatal famine and Schizophrenia. Upload your DAG here.
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This response will be reviewed and graded after submission.
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Question 10 of 27
10. Question
10. The authors of the original study then published a reply to the commentary (Susser 1997). Please read this article (particularly focus on the first reason they provided), and summarize why confounding by social class may not be a big concern?
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Question 11 of 27
11. Question
11. Add +/- symbols to your DAG from question 9 based on the authors’ response and comment on the direction of potential confounding by social class. Upload your revised DAG here.
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Upload your answer to this question.
This response will be reviewed and graded after submission.
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Question 12 of 27
12. Question
Please review the following and then answer Questions 12-19.
The Rochester Birth Cohort is a retrospective, closed cohort of all children born from 1976 through 1982 in Rochester, Minnesota. Using this cohort, investigators were interested in the association between preterm vs full term live birth and the risk of developing asthma by age 7. Below is hypothetical data for the association between preterm vs full term live birth and asthma during the 7-year study period stratified by maternal smoking during pregnancy. No participants were lost to follow-up.
12. Calculate the cumulative incidence ratio for the crude association between preterm vs full term birth and asthma in this cohort. Interpret your result.
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Question 13 of 27
13. Question
13. The authors were concerned about confounding by maternal smoking during pregnancy. What are the properties maternal smoking must have to be a confounder?
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Question 14 of 27
14. Question
14. Using the data in the tables above, calculate a measure of association to assess the relationship between maternal smoking during pregnancy and asthma among children who were born full term.
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This response will be reviewed and graded after submission.
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Question 15 of 27
15. Question
15. Using the data in the tables above, calculate a measure of association to assess the relationship between maternal smoking during pregnancy and birth term in the study base.
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Question 16 of 27
16. Question
16. Assuming maternal smoking during pregnancy is not a downstream consequence of birth term or asthma. Based on your answers to question 14 and 15, do you think maternal smoking is a confounder for the association between birth term and asthma? Why or why not?
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This response will be reviewed and graded after submission.
Grading can be reviewed and adjusted.Grading can be reviewed and adjusted. -
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Question 17 of 27
17. Question
17. Assuming that maternal smoking during pregnancy is a confounder, could adjusting for maternal smoking change the crude association between birth term and asthma? If so, in what direction would you expect the change?
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This response will be reviewed and graded after submission.
Grading can be reviewed and adjusted.Grading can be reviewed and adjusted. -
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Question 18 of 27
18. Question
18. Draw a DAG to support your argument from Question 17, above. Use the (+) symbol and the (-) symbol to indicate the direction of the association between the variables based on your answers to questions 14 and 15.
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This response will be reviewed and graded after submission.
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Question 19 of 27
19. Question
19. Calculate the cumulative incidence ratio for the association between preterm vs full term birth and asthma separately for mothers who smoked during pregnancy and mothers who did not smoke during pregnancy. Comparing the stratum-specific CIRs to the crude CIR in question 12, is the direction of bias consistent with what you answered in question 17?
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Question 20 of 27
20. Question
How much time did you spend on this homework?
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Question 21 of 27
21. Question
Please include here any questions from the recorded lectures or homework that you would like to be addressed during the lab session.
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Question 22 of 27
22. Question
Your feedback is important to us. So that we can adequately adjust the lecture materials, please answer the questions below relating to each of this week’s topics:
Part 1: Directed Acyclic Graphs
Was the amount of information presented too little, just right, or too much?
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Question 23 of 27
23. Question
The lecture’s contents were clearly explained.
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Question 24 of 27
24. Question
How was the pace of the lecture?
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Question 25 of 27
25. Question
Your feedback is important to us. So that we can adequately adjust the lecture materials, please answer the questions below relating to each of this week’s topics:
Part 2: Confounding
Was the amount of information presented too little, just right, or too much?
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Question 26 of 27
26. Question
The lecture’s contents were clearly explained.
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Question 27 of 27
27. Question
How was the pace of the lecture?
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