4.11.If you wanted to examine the association of a high-fat diet with bowel canc

Question

4.11.If you wanted to examine the association of a high-fat diet with bowel cancer, briefly outline a potential study for each of the following designs:

• Ecological study

• Cohort study

• Intervention study

• Case-control study

At a local health clinic, 300 women were screened for HIV infection; 100 women who were HIV positive were compared to 200 women who were HIV negative. All women were interviewed with respect to their recent history of sexual partners: 60 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-Calculate the odds of having a partner who is an IV drug user among women who are HIV positive.

B-Calculate the odds of having a partner who is an IV drug user among women who are HIV negative.

C- Calculate the odds ratio for the association between having a partner who is an IV drug user and HIV infection.

D- Interpret the strength of the association you computed in part C.

Epidemiology questions from Epi class.

Explanation / Answer

A-Calculate the odds of having a partner who is an IV drug user among women who are HIV positive.

Answer :

Number of women who are HIV positive = 100

Having a partner who is an IV drug users among HIV positive women = 60

Not having a partner who is an IV drug users among HIV positive women = 100 - 60 = 40

so odds = 60:40 = 3:2 = 3/2

(B)

Number of women who are HIV negative = 200

Having a partner who is an IV drug users among HIV negative women = 25

Not having a partner who is an IV drug users among HIV negative women = 200 - 25 = 175

so odds = 25:175 = 1:7 = 1/7

(C) Odds Ratio = (a/c) / (b/d)

Where

so Odds Ratio = 60 * 175/ 25 * 40 = 10.5

D. Here we can see that the there is (10.5 - 1) * 100 = 950% more chance to get affected.

so strenght of association is too strong.

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