How are data files used in research?
Since the early 1940's social scientists have collected and analyzed data as part of a quantitative approach to research. When you use data from an archive of previously collected surveys you are engaged in secondary analysis of primary information. Secondary analysis is a great way to do research, especially if you are a student. Designing your own survey is not trivial and the cost to carry out even a simple survey can be quite prohibitive in terms of cost.
Beyond cost, there are other excellent reasons to do research using previously collected data. For example, you might read about the results of a survey on a subject of interest to you. The public opinion polls conducted by media organizations such as the New York Times or CBS News are examples of such surveys. If the data are available from an archive, (such as ICPSR) you might decide to analyze the data with the same statistical procedures used by the original data collectors. By replicating the work of another researcher, you can test the validity of the previous analyses.
Data files are used to test research hypotheses about people's attitudes and behaviors. For example, you might want to test your idea that a higher level of education leads to a higher income level. Comparing years of schooling with a person's wage or salary, is one way to better understand the relationship between education and income attainment. Of course this is a very simple comparison and there are many other factors to consider. If you are interested in this topic, take a look at the data available from High School and Beyond: A Longitudinal Survey of Students in the United States.
There are many methods used to conduct surveys. Questionnaires can be organized in a number of ways, and the design can affect how people respond to questions. Some social scientists analyze similar data collected in several surveys to understand how different survey methodologies change the kind and quality of data collected. Other researchers study the methods used to identify sample populations, and still others are interested in how the interview setting can affect people's responses. For example, there may be differences depending on whether the questionnaire is sent by mail, is conducted on the telephone, or if the survey is conducted through the internet or using a mobile device. Data are gathered in the UCLA Los Angeles County Social Survey by telephone. The Hispanic Health and Nutrition Examination Survey is conducted by personal interview. Questionnaires are sent by mail in conducting the U.S. Decennial Census.
Compare Population Groups
Research using surveys is useful for studying the attitudes and behaviors of different population groups. For example, you might want to study the music preferences of teenagers vs those who are age 65 and above. Or, perhaps you have an interest in understanding the differences between Republican and Democratic voters. Populations from different countries and cultures can also be studied using secondary analysis techniques. Some examples of such studies are the American National Election Study (ANES), the General Social Survey (GSS), or the International Social Survey program (ISSP).
In another area of social science research, changes in attitudes and behavior are studied over time. There are two approaches commonly used. In longitudinal analysis, the same respondents are studied repeatedly for a specified period of time. Some data files in the Archive are longitudinal studies of high school students, of the occupational change of members of the same households, or of changes in the amount and kind of income people receive over time. Examples of these are National Education Longitudinal Survey (NELS), Panel Study of Income Dynamics (PSID), or Survey of Income and Program Participation (SIPP).
A second approach is called cross-sectional analysis. Using this method, people are interviewed only one time, but the same questionnaire is used repeatedly, with different respondents, over a specified period of time. Here, methods used in determining the group of people, or sample, to be interviewed are of great importance. Special care is taken to be sure the groups are similar in number, gender, race/ethnicity, age, and in geographic location. In cross-sectional studies, changes in attitudes and behavior are studied by analyzing data gathered at discrete points. Examples of data files which can be used for cross-sectional analysis are The California Polls, the Current Population Survey: Annual Demographic File, and the National Survey of Family Growth.
Social science research uses many terms which may be new to you. For more information on terms such as are used in this web site, you might want to explore a glossary created and maintained by Jim Jacobs, Data Consultant.