ISR Social Science Data Archive

Data Tutorial

This tutorial will provide guidance on searching for and using Archive materials. 

What is Social Science Data?

Social Science Data Files are primary source materials encompassing raw data files and textual or electronic format documentation, normally called codebooks.  Data files are not eye-readable.  A raw data file is composed of characters or numbers on which mathematical operations are carried out using a statistical program (for example, using SPSS, SAS, or STATA), on a computer (such as your personal computer, or one of the campus computer center facilities), and interpreting the results of statistical processing.  If you printed out a raw data file, it would look like this.  Below is a visual on how data is incorporated into the research process.

                                             Image showing relationship between collecting data, data analysis and publications

  How are data files used in research?

*** Secondary Analysis
*** Replication
*** Test Hypotheses
*** Evaluate Methodology
*** Compare Population Groups
*** Longitudinal or Cross-Sectional Analysis 

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.  The cost to carry out even a simple survey can be quite prohibitive in terms of cost.  For example, as of January 1999, an in-person survey of 1000 respondents with about 50 questions, conducted in Los Angeles County, would cost between $150 - $300 per respondent!  Below are just a few examples of common secondary analysis techniques. 

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. 

Test Hypotheses
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. 

Evaluate Methodology
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 by personal interviews.  Data are gathered in the  ISR 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)

Longitudinal Analysis
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).

Cross-Sectional Analysis
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. 

When should I use data instead of a printed resource?

Data files do not always need to be used to answer research questions.  In fact, you may want to use a range of data files, published statistics, and reports for your research. Information from raw data files is often already processed into published tables and explanatory reports.  Tables and reports can be found in publications stored in libraries, and increasingly, over the Internet. Many numeric information resources are available through online tools for creating customized tables. An example of an online tool is the Census Bureau's American Factfinder. However, for detailed answers to questions, statistically analyzing data can be the best approach.  Here are some points to consider when deciding what kind of format will work best for your research: 

*** Several layers of geography are easier to process in a data file. 
*** Small geographic areas, such as tracts or blocks are usually only found in data files. 
*** Data files are usually needed for longitudinal and cross-sectional analyses. 
*** Data files are best for detailed race and ethnicity tabulations. 
*** Printed reports will usually contain the most recent information. 
*** Historical information will often only be found in printed tables and reports. 
*** Online tools will usually generate aggregate tables as well as maps.
*** Online tools are best for one or two specific geographic areas, such as two counties, or two cities. 

For more information, be sure to review the sections of this web site on What is a Codebook and on Searching for Data.

How do I look for data?

There are different ways to think about data to be used in research. First is the type of data needed to address a research question. Next a review of the study documentation such as questionnaires and codebooks will help determine which data will useful. Here is a visual of ways to think about the kinds of sources where you can find data.

                                                             Image of news articles, scholarly articles, statistical sources, data sources and data analysis

 You can look for information in the popular press discussing recent studies.  You can find news articles in indexes of newspapers and by using Lexis Nexis.  The UCLA Library has access to LexisNexis – you can also search by various newspaper indexes, such as the New York Times or use periodical indexes.

Sometimes we read about things in the news and we want to have something more extensive. For this, we can use the article databases to locate analyses and find research about studies discussed in the news.   Example:  Social Sciences Citation Index which is part of the content licensed to UCLA through ISI Web of Knowledge.

But maybe we want to find some more detail from the articles we read – sometimes information in tabular form – tables, charts, etc. can be useful.  Government sites provide a great deal of statistical information – remember to use local, state, and national government sites. Example: the LA County Election Office you might use a statistical abstract for both the US and/or for individual states.

Sometimes we look at a chart or a table and we want to know about the data that created the table – so here we are talking about the raw data –For the work you will be doing in this course you will find data in the Data Archive, at ICPSR or from other sources.  Sometimes the codebook or other materials that are the eye-readable guide to the data are as useful as the data files.

Finally, sometimes you won’t have the data points you seek until you actually analyze your data with a software tool or statistical package.

Next, it is important to be aware for the units of analysis, types of variables, and the data structure or format. These are described below.

Units of Analysis

What is the unit of measurement in the data file? Examples might be: 
Why is this important? Let's say you want to look at the income of each person in a household. A study which is organized with only household level of information will not be useful to you since it will not provide income amounts for individuals. Keep in mind that some data files have more than one type of unit of analysis or measurement. 

Types of Variables

*** Alpha or Character vs. Numeric 
*** Continuos vs. Discrete 
*** Summary or Aggregate vs. Micro 
It is necessary to understand the types of variables available in data in order to perform correct statistical analysis procedures. 


*** Alpha -- refers to data that is in text format. 
*** Continuous -- represents a 'real' piece of information, such as age in actual years, or income in actual dollars. 
*** Discrete -- a coded numeric representation of information (i.e. persons who answered (1) have incomes in the $10,000 to $15,000 range). 
*** Micro -- a data file containing information about individuals or individual units; organized for analysis by single units. 
*** Numeric -- refers to data that are coded responses to questions. 
*** Summary or Aggregate -- Data that have been tabulated or averaged or in some way combined such that single units of data cannot be evaluated. 

Data Structures

Finally, you need to study the codebook to determine the physical format of the file as it is arranged electronically. You will need to describe this arrangement in your statistical analysis. In SPSS, this description will appear in the DATA LIST. In SAS, this will be part of your INPUT statement. The three most common structures are: Rectangular, Hierarchical, and Relational

This is the most common form of data structure. In a survey, the answers given by each respondent are arranged in the same order. If the data were printed, it would resemble an array of persons and responses to questions, as illustrated. 

These file are also described as having a tree-like structure. Data in this example are organized by household. Within households, it is possible to study individuals, and for each individual is possible to study sources of income. Data items are linked via their household identification. 

The most common form of a relational file, is one created using a spreadsheet package. In this example, there is a household file, a person file, and an income file. Each of these may be analyzed separately from the others. The files are linked by keys, or identification pointers. For example, there is an identifier for persons and income in the household file, and so forth.



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