1.What is the differencebetween individual- and population-based studies? How is this reflected in theecological study hypotheses?Individual based studiesexamine how exposure and disease affect an individual person on a case by casenature without including the community as a whole. The aim is to determinedifferences within individuals of the same population. An example fromthe epiville module would be to look at the employees of the Porks-a-lot pigfarm and see if they have a higher risk of developing Susser Syndrome comparedto the rest of the population of Epiville. Population based studies lookat specific populations of people and how exposures and disease are impactingthat specific population. This is reflected in the ecological studyhypotheses because it is determining Susser Syndrome cases based on incidenceof being serviced by the Rothman Reservoir or the Greenland Reservoirpopulation.
The units for ecological studies are “populations or groupsof populations rather than individuals.” Our hypothesis is that RothmanReservoir will have a high incidence of Susser Syndrome cases compared to theGreenland Reservoir population. This comparison involves a populationbeing serviced by Rothman and a population being serviced by Greenland. 2. Think of anexposure/disease relationship that you are interested in studying.
Describe anindividual-level study AND an ecological study that you could conduct toexamine the associations between the exposure and the outcome. Specifyhypotheses and design elements (individual and ecological).The exposure/diseaserelationship that I am interested in studying is the correlation between HPVand the development of cervical cancer.
For an ecological study, Iwould look at publically available data on HPV and compare them to compare themto incidence of cervical cancer across regions of the United States. Myhypothesis would state that there is a mutual relationship between highprevalence of HPV and the incidence of cervical cancer.For an individual-levelstudy, I could do a case-control study and get participants to join the studyfrom the local hospital. I would enroll patients that had cervical cancerand patients that did not have cervical cancer. From there, I wouldcompare the women that had the disease to the women that did not have thedisease.
My hypothesis would be that the women from the group that hadcervical cancer had possible risk factors (such as HPV) that resulted in thedevelopment of cervical cancer. I would be able to look at the manydifferent exposures of the two groups and see what happened in the past. 3. What is meant byecological fallacy? Give two examples.
An ecological fallacy is whenwe try to use statistics/characteristics that we have collected on a populationlevel and try to apply it on an individual level. An inference is made aboutindividuals based on the data that was obtained from the population. From our ecological study wedetermined there was an increase in Susser Syndrome cases in the populationthat is serviced by Rothman Reservoir. If we then went on to say thatindividuals that were drinking the water from the Rothman Reservoir has doublethe chance of developing Susser Syndrome than the individuals that weredrinking the water from the Greenland Reservoir, this would be an example of anecological fallacy.
We are making an inference about the individual basedoff the information of that we obtained from the population, even though it hasnot yet been proven. Another example is that ithas been documented that there has been a large increase in autism in the groupon children that receive vaccinations since 1998 (lecture notes: Cross-sectionalstudies). It would be an ecological fallacy if we were to say thatvaccine use causes autism, since on the individual level it has been proventhat this is not the case.