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Old 08-07-2012
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Stats What methodology to study correlation?

A group of investigators plans a cohort study to examine the association between beta carotene exposure and the incidence of lung cancer. What methodology should they adopt?

a) Correlate dietary intake of beta carotene with lung cancer incidence
b) Examine the history of beta carotene intake in groups with and without lung cancer
c) Examine the occurrence of lung cancer in in groups randomly assigned to receive supplemental beta carotene or placebo
d) Follow a group with high dietary intake of beta carotene to determine future incidence of lung cancer
e) Follow groups groups with high or low dietary intake of beta carotene to examine the occurrence of lung cancer
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Old 08-07-2012
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its c.
b is case-control study
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Old 08-07-2012
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For cohort, you need subjects and a risk factor and a follow over time. Placebo and the risk factor should be applied, so I go with c.
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d , and please tell the source of question, thank you
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Old 08-07-2012
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b) Case-control study

waiting for cancer to occur would take too much of a time
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Old 08-08-2012
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Correct Answer correct answer

The answer is e) Follow groups groups with high or low dietary intake of beta carotene to examine the occurrence of lung cancer

A cohort study follows groups exposed (high dietary intake of beta carotene) and unexposed (low dietary intake of beta carotene) to the suspected risk factor to observe differences in incidence of the outcome (lung cancer).

As for B) - Because it assesses frequency of exposure to the suspected risk factor in groups with and without the outcome, this is a case-control study. And the investigators wanted to run a cohort study.

As for C) - Because the investigators determine exposure to the intervention, this is a placebo-controlled clinical trial. And the investigators wanted to run a cohort study.

As for D) - Although one group is being followed to determine future incidence of a disorder, the lack of an unexposed or comparison group indicates that this is not a cohort study.
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Old 08-08-2012
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Quote:
Originally Posted by Casandra View Post
The answer is e) Follow groups groups with high or low dietary intake of beta carotene to examine the occurrence of lung cancer

A cohort study follows groups exposed (high dietary intake of beta carotene) and unexposed (low dietary intake of beta carotene) to the suspected risk factor to observe differences in incidence of the outcome (lung cancer).

As for B) - Because it assesses frequency of exposure to the suspected risk factor in groups with and without the outcome, this is a case-control study. And the investigators wanted to run a cohort study.

As for C) - Because the investigators determine exposure to the intervention, this is a placebo-controlled clinical trial. And the investigators wanted to run a cohort study.

As for D) - Although one group is being followed to determine future incidence of a disorder, the lack of an unexposed or comparison group indicates that this is not a cohort study.

in this case you won't have any unexposed group ! or there is it something else? bit confused
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Quote:
Originally Posted by Dr.Lacune View Post
in this case you won't have any unexposed group ! or there is it something else? bit confused
they took the group with low dietary carotene intake as a control group.
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Old 08-08-2012
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Tricky question!
And Casandra, great questions as usual! Thank you!
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Old 08-09-2012
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can you explain more on choice C, still dont know what diff. thanks
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Old 08-09-2012
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Ahhh I didn't read the question right. I totes skipped the "cohort" part of it
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