1.What would state that there is a mutual

1.What is the difference
between individual- and population-based studies? How is this reflected in the
ecological study hypotheses?

Individual based studies
examine how exposure and disease affect an individual person on a case by case
nature without including the community as a whole. The aim is to determine
differences within individuals of the same population.  An example from
the epiville module would be to look at the employees of the Porks-a-lot pig
farm and see if they have a higher risk of developing Susser Syndrome compared
to the rest of the population of Epiville.  

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Population based studies look
at specific populations of people and how exposures and disease are impacting
that specific population.  This is reflected in the ecological study
hypotheses because it is determining Susser Syndrome cases based on incidence
of being serviced by the Rothman Reservoir or the Greenland Reservoir
population.  The units for ecological studies are “populations or groups
of populations rather than individuals.”  Our hypothesis is that Rothman
Reservoir will have a high incidence of Susser Syndrome cases compared to the
Greenland Reservoir population.  This comparison involves a population
being serviced by Rothman and a population being serviced by Greenland.

 

2. Think of an
exposure/disease relationship that you are interested in studying. Describe an
individual-level study AND an ecological study that you could conduct to
examine the associations between the exposure and the outcome. Specify
hypotheses and design elements (individual and ecological).

The exposure/disease
relationship that I am interested in studying is the correlation between HPV
and the development of cervical cancer.  

For an ecological study, I
would look at publically available data on HPV and compare them to compare them
to incidence of cervical cancer across regions of the United States.  My
hypothesis would state that there is a mutual relationship between high
prevalence of HPV and the incidence of cervical cancer.

For an individual-level
study, I could do a case-control study and get participants to join the study
from the local hospital.  I would enroll patients that had cervical cancer
and patients that did not have cervical cancer.  From there, I would
compare the women that had the disease to the women that did not have the
disease.  My hypothesis would be that the women from the group that had
cervical cancer had possible risk factors (such as HPV) that resulted in the
development of cervical cancer.  I would be able to look at the many
different exposures of the two groups and see what happened in the past.  

3. What is meant by
ecological fallacy? Give two examples.

An ecological fallacy is when
we try to use statistics/characteristics that we have collected on a population
level and try to apply it on an individual level.  An inference is made about
individuals based on the data that was obtained from the population.  

From our ecological study we
determined there was an increase in Susser Syndrome cases in the population
that is serviced by Rothman Reservoir.  If we then went on to say that
individuals that were drinking the water from the Rothman Reservoir has double
the chance of developing Susser Syndrome than the individuals that were
drinking the water from the Greenland Reservoir, this would be an example of an
ecological fallacy.  We are making an inference about the individual based
off the information of that we obtained from the population, even though it has
not yet been proven.

Another example is that it
has been documented that there has been a large increase in autism in the group
on children that receive vaccinations since 1998 (lecture notes: Cross-sectional
studies).  It would be an ecological fallacy if we were to say that
vaccine use causes autism, since on the individual level it has been proven
that this is not the case.