Ecological Study

Data
Collection

Step 5: Data Collection

Ecological studies involve comparison and analysis of variables at the population level. They may involve direct observations of individuals which are then aggregated or summarized (to give means or proportions) or they may rely on global population measures, such as population density. The data to be used in an ecological study have typically been collected previously for other purposes and often come from such sources as population censuses and disease registries.

Your study is no exception. Rather than collecting data via fieldwork, you will journey through the often treacherous terrain of paper-based registries and computer databases. Before you begin, you must understand exactly the kind of information you are looking for so that you can narrow down the number and type databases/registries to examine.

3.	On a conceptual level, define the minimal information you need to collect in order to test your ecological study hypothesis.
		a.	I will need to know the size of the population of Epiville and the number of new cases of Susser Syndrome at the present time.
		b.	I will need to know the number of new cases of Susser Syndrome and the size of the populations serviced by the Rothman and Greenland reservoirs.
		c.	I will need to know the number of new cases of Susser Syndrome as well as their addresses. Additionally, I will need to know the geographic areas serviced by the Rothman and Greenland Reservoirs, respectively. Finally, I will need to know the population size of these areas and the amount of reservoir water used during a given time period.

In order to get the information on the reservoirs, you contact the Epiville Water Works Department. They report that all of Epiville is serviced by either the Rothman or Greenland Reservoir. The geographic area served by each reservoir is subdivided into 5 sectors. The Water Works Department has a database recording the average daily water use for each sector (but not for each individual living in the sector) for each of the previous 5 years. You decide that the information regarding the most recent year is adequate.

Additionally, you have access to the most recent Epiville population census.

Finally, the Epiville Department of Health keeps a database of all reportable diseases. Susser Syndrome is reportable and as such all physicians and hospitals must report each diagnosed case along with the requisite demographic information to the health department.

4.	How can all of this information be used to test your study hypothesis?
		a.	I can cross-reference the three databases in such a way that I will know from what reservoir sector the Susser Syndrome cases came, the population size of that sector, and the average daily water use of that population.
		b.	I can use the Water Works Department information to extrapolate the amount of water each individual in Epiville consumed and then cross reference these individuals with the Susser Syndrome registry.

5.	Which of the following is a chief shortcoming of using a reportable disease registry to collect Susser Syndrome cases in our study?
		a.	We may not capture all of the Susser Syndrome cases occurring in Epiville.
		b.	We would only be capturing prevalence data and not incidence data.
		c.	We are relying on the diagnostic capabilities of the doctors and hospitals and are assuming that a case reported and recorded as Susser Syndrome is in fact such.

The next step is to cross-reference your databases and extract the required information. Being no fool, you call in the database experts to help you. After a few days of computer wrangling, the databases appear to be linked and you can run your search queries.

Learning
Objectives

Introduction
to Study

Data
Collection