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Old 08-07-2012
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Default Which type of study is that?

A study finds that cities with greater air pollution have lower mean birthweight. What is the design of this study?

a) Case-control study
b) Cohort study
c) Cross-sectional study
d) Ecological study
e) Prevalence study

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Old 08-07-2012
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Haven't did biostat yet. I am posting this comment to get update about this post.
Mean while I always have confusion understanding these terms properly. So if someone can explain them in layman language that would be great.


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Old 08-07-2012
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I am going with a) Case-control
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Old 08-07-2012
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cross sectional is correct
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Old 08-07-2012
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stem of the question suggests that

"cities with greater air pollution(risk factor) have---------> lower mean birthweight( disease)"
sounds like something is being compared in prospective so i will go for B

(plus no one was picking this option so adding variety to suggested answer)
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Old 08-07-2012
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i believe question should atleast provide direction of research conducted.as it not than we left with option of cross sectional study
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Old 08-07-2012
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I agree

Quote:
Originally Posted by Kabutar111 View Post
i believe question should atleast provide direction of research conducted.as it not than we left with option of cross sectional study
I agree with you...... question is non specific and it can be taken in any direction also as far i as i remember cross sectional = prevalence study so option c&e are essentially same
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Old 08-07-2012
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a) Case-control study, sounds retrospective, to me.
lbw babies - cases and normal ones - controls
comparing the effect of pollution and arriving at a decision.
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Old 08-07-2012
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A...observational+ retrospective=case control study
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Old 08-08-2012
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Default correct answer

The answer is d) Ecological study

One key to identifying an ecological study is that the unit of analysis is a group rather than a person. In this study, investigators compare the level of air pollution and mean birth weight in different cities. The unit of analysis is a city. Investigators have no knowledge of either variable for any one person.

As for A) - In case-control studies, individual persons are the unit of analysis. Groups are defined on the basis of outcome (or disease) status. The frequency of exposure in the cases is compared with the frequency of exposure in the controls.

As for B) - In cohort studies, individual persons are the unit of analysis. Groups characterized by the exposure or nonexposure to a suspected risk factor are followed for the occurrence of the outcome.

As for C) - At first glance, this study can appear to be a cross-sectional study because it compares level of air pollution and birth weight at one point in time; however, in cross-sectional studies, individual persons are the unit of analysis.

As for E) - A prevalence study is a type of cross-sectional study. As such, it uses individual persons as the unit of analysis.
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Kabutar111 (08-08-2012), koolkiller88 (08-08-2012), venky2600 (08-10-2012)



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