Existing Data as a Measurement Tool

Finding Existing Data

Survey research and experimentation are original data collection methods. Original data collection methods are “original” because they are collected by the researcher and do not exist prior to this collection process. With existing data, “someone else” has collected the data. The key here is that a researcher must “find” these existing data. Often overlooked is the fact that scientifically reliable and valid data may already exist. Prior to collecting any original data via surveys or experiments, a researcher should first determine if data pertaining to their research project already exists.

Existing Data Example 1

I want to use one of my research papers as an example of how an entire project can be done using existing data sources. I began with the following research question: Do municipalities that maintain their own police force versus those that contract with adjacent municipalities for police services have lower non-violent crime rates? The UoA is municipalities, specifically New Jersey state municipalities. The IV is the type of police force and the DV is non-violent crime rates. EV’s include, but are not limited to: municipal population, population density, the percent of the population that is male ages 15 to 24, percent of female headed households, the distance from the cities Newark or Camden (whichever is less), and the poverty rate. All of these variables were measured using an existing data source. Multiple existing data sources were pooled – or combined – to create one data set that served to answer my research question.

Let us start with the dependent variable non-violent crime. I was directed to the New Jersey State Police (NJSP) website subsequent to an Internet keyword search using the following search phrase: “New Jersey towns and non-violent-crime rates.” On the main page of the NJSP website, there is a drop down menu under the heading “Public Information.” When clicking on this drop down menu, you will see a sub-heading entitled “Crime Reports and Stats” (highlighted in Figure 1). When clicking on the sub-heading “Crime Reports and Stats,” you are then directed to the Uniform Crime Reports (UCR) of the Federal Bureau of Investigation (see Figure 2).

Figure 1.

New Jersey State Police

Figure 2.

New Jersey State Police – crime data

For this research paper, I used 2007 data because it was the most recent at the time. When clicking on the 2007 UCR Report, you are directed to the data’s table of contents. If you scroll down the page, you will see a sub-heading that reads “New Jersey Municipal-County Offense and Demographic Data.” Clicking on this link leads you to the non-violent crime rate data (see the far right column of Figure 3).

Figure 3.

Uniform Crime Report – Federal Bureau of Investigation (New Jersey municipalities)