# Epidemiology 6

**PH 3120 Homework Assignment #6**

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**DIRECTIONS: ** Please answer the following questions on a separate piece of paper. Include your name and CIN number on your homework assignment. Students are welcome to work in groups to complete homework assignments. However, each student must submit his/her own answers to receive credit. SHOW ALL OF YOUR WORK!

All of the following questions are in relation to the following journal article which is available on Moodle: *Parr CL, Magnus MC, Karlstad O, Holvik K, Lund-Blix NA, Jaugen M, et al. Vitamin A and D intake in pregnancy, infant supplementation and asthma development: the Norwegian Mother and Child Cohort. Am J Clin Nutr 2018;107:789-798.*

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**QUESTIONS: **

- Create a 2X2 table to compare the risk of asthma among infants supplemented with cod liver oil SOMETIMES to NEVER supplementing infants with cod liver oil.
- Calculate the risk of asthma among infants supplemented with sometimes with cod liver oil and calculate the risk of asthma among infants never supplemented with cod liver oil.
- Calculate the unadjusted relative risk comparing the risk of asthma for infants supplemented with cod liver oil sometimes to infants never supplemented with cod liver oil.
- Calculate the 95% confidence interval associated with the unadjusted RR that you calculated in #3.
- What is the formula for the lower limit?
- Calculate the ln(RR).
- Calculate the standard error of the ln(RR)
- Calculate the lower limit of the 95% CI.
- What is the formula for the upper limit?
- Calculate the upper limit of the 95% CI.

- Present the unadjusted RR and 95% CI and state the meaning of the 95% CI.
- Based on the 95% CI, is the unadjusted RR statistically significant? How do you know?
- Sketch the p-value function for the point estimate and 95% CI that you calculated.
- If you had calculated a 90% CI, would it be wider or more narrow than the 95% CI that you calculated?