Homework#7_2019EPI
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EPID/CPH 309: Introduction to Epidemiology
Exercise # 7: Study Design & Measures of Effect-Due
November 4
th
Makenna Mercer 1.
At a local health clinic, women were screened for HIV infection; 100 women were identified who were HIV positive and another 300 women who were recruited into the study who were HIV negative. All women were interviewed with respect to their recent history of sexual partners: 65 of the infected women had a sexual partner within the last 2 years who was an intravenous drug user, while 25 of the uninfected women had a sexual partner in the last 2 years who was an intravenous drug user.
a.
What is this study design? Cohort
b.
Construct a 2 x 2 table of the outcome and the exposure. Label the table. Left side (Exposure) Top (HIV)
Yes
No
Yes
65
25
No
35
275
c.
Calculate the odds ratio for the association between having a partner who is an IV drug user and HIV infection.
(65/35)/(25/275) = 1.8/.09= 20% d.
Interpret the strength of this association. There is a relatively weak association between the two which would be 20%. 2.
The families of 6 cancer cases who used to work at a particular large office site believe there is a cluster of cancer as a result of unsafe building materials in the old buildings. This company also has new building that don’t use these unsafe materials. You collect Homework #8
1
information from employment records on all the people that worked for this company for the last 25 years regarding which building they worked in. You then tried to figure out
who had developed cancer.
a.
What is the study design? Cohort Study b.
If the employer doesn’t have health records for the employees; name a good source for finding if any of the employees developed cancer.
One could either send out a survey to the workers or conduct an interview. c.
After reviewing your data source on cancer cases, you find that there were 52 people
developed cancer of the 684 that worked in these old buildings. You also found 22 cases among the 294 employees that had worked in the new buildings. Construct a 2x2 table. Exposure (left side) Disease Yes
No
Yes
52
632
No
22
272
d.
Should you calculate a RR or an OR for this study design?
RR
e.
Use the appropriate test (either OR or RR) to determine risk. 52/(52+632)/22(22+272)= .076/.074= 1.02
f.
Interpret your result. Old buildings are not causing cancer. g.
Calculate an AR% and provide an interpretation. 684-294= 390/52= 7.5X 100= 750 Homework #8
2
h.
Do you think these old buildings are causing this cancer?
I do not think the old buildings are causing the cancer. Homework #8
3
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