The cruise ship owners contacted the CDC to conduct an in-depth analysis of the
ID: 3041780 • Letter: T
Question
The cruise ship owners contacted the CDC to conduct an in-depth analysis of the possible modes of transmission of the Rotavirus in the cruise ship environment. CDC investigators interviewed all of the passengers on the last affected cruise (N=3,000) and obtained information on their activities. They found the following results: 1,000 passengers had gone swimming in the upper deck pool and 2,000 passengers had never gone swimming in the upper deck pool. 100 of the passengers who swam in the upper deck pool and 100 of the passengers who did not swim in this pool developed Rotavirus gastroenteritis during the cruise. FYI: The cruise lasted one week.
3. Set up the two by two table for these data.
Developed gastroenteritis
Did not develop gastroenteritis
Total
Ever swam in pool
Never swam in pool
Total
Calculate the risk ratio of gastroenteritis associated with swimming in the upper deck pool.
State in words your interpretation of the above risk ratio.
Calculate the risk difference in the above example.
State in words your interpretation of the above risk difference.
8. What measure of disease frequency are you using to calculate the risk ratio and risk difference?
9. What measure of association should be used to answer the question, “How many additional cases of Rotavirus gastroenteritis among all cruise passengers (N=3,000) was associated with swimming in the upper deck pool?”
10. (EXTRA-CREDIT!!!! – 5 points) When the cruise ship owners examined the findings of the CDC investigation, they stated that the crude results were invalid because of the age differences between the people who swam in the upper deck pool and those who did not. Examine the following table and state whether or not you agree with the cruise ship owners.
Age Groups (years)
Swam in Upper Deck Pool
Never Swam in Upper Deck Pool
10-20
25%
10%
21-30
20%
10%
31-40
20%
15%
41-50
15%
20%
51-60
10%
20%
>60
10%
25%
Total
100%
100%
a. Based on these data, do you agree or disagree with the assessment that the crude results were invalid? Briefly justify your answer.
b. Regardless of whether you agree with the cruise ship owners, explain in at least 3 sentences the method that epidemiologists use to account for age differences in populations. Be sure to mention what additional data would be needed to perform this procedure in the Rotavirus cruise study.
Developed gastroenteritis
Did not develop gastroenteritis
Total
Ever swam in pool
Never swam in pool
Total
Explanation / Answer
Developed gastroenteritis
Did not develop gastroenteritis
Total
Ever swam in pool
100
900
1000
Never swam in pool
100
1900
2000
Total
200
2800
3000
risk ratio of gastroenteritis associated with swimming in the upper deck pool = 100/1000/(100/2000) =2
Risk of developing gastroentites for people who swim in upper deck pool is twice than in people who dont swim.
RIsk difference = 2-1/1 =1=100%
Swimming in the upper deck pool increases risk of developing gastroentities by 100%
Please repost the other parts individually.
Developed gastroenteritis
Did not develop gastroenteritis
Total
Ever swam in pool
100
900
1000
Never swam in pool
100
1900
2000
Total
200
2800
3000
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