Sample Data Files

Data come in many different formats, encoding schemes and structures. This page shows samples of several typical data types, with SPSS and SAS programs to analyze each sample. A "Key to Terminology" used in this listing follows the file links.

These sample files are used in the ITS workshop "Dealing With Data", which is part of the ITS workshop series each semester. The course can be taught also by special request. The class includes a presentation of search strategies and worldwide sources on the WWWeb, which are summarized in:

www.usc.edu/its/doc/statistics/help/multiuse/datasamples/netresources.shtml

Raw ASCII -- rectangular, free format (sample contains both numeric and character values)

Data File -- SPSS program -- SAS program

Raw ASCII -- rectangular, fixed format (sample contains both numeric and character values)

Data File -- SPSS program -- SAS program

EBCDIC -- (fixed format used for this sample)

Data File -- SPSS program -- SAS program
NOTE: Data file requires binary mode download (see instructions below)

Hierarchical -- (example taken from U.S. Census PUMS files)

Data File -- SPSS program -- SAS program

Comma-Delimited

Data File -- SPSS program -- SAS program
NOTE: In addition to the program method shown here, SAS for Windows also can read Comma-delimited data using the "Import Wizard"

Excel/Access (.xls) files

Data File -- SPSS (Windows) program -- SAS (Windows) program
NOTE1: Data file requires binary mode download (see instructions below)
NOTE2: After downloading, rename the data file (if necessary) from database.xlsfile to database.xls
(alternative *.xls file)

Tab-Delimited

Data File -- SPSS (Windows) program -- SAS program
NOTE1: In addition to the program method shown here, SAS for Windows also can read Tab-delimited data using the "Import Wizard"
NOTE2: SPSS for UNIX (Version 6.1) cannot read Tab-Delimited files; for an alternative, see:
http://www.usc.edu/its/doc/statistics/spss/faq/tabdelimited.html

System Files

SPSS Save File -- SPSS Program
SAS (Windows) Data Set -- SAS (UNIX) Data Set -- SAS Program
NOTE1: Data files require binary mode download (see instructions below)
NOTE2: System Files will appear as garbage or empty, or the browser will not open them at all, giving you a download dialog box instead. They should download OK.

SPSS Portable File

Data File -- SPSS program
NOTE1: SPSS Portable files require ASCII mode (standard) download, not binary.
NOTE2: After downloading, rename the data file (if necessary) from spss.transport to spss.por

SAS Transport File

Data File -- SAS program
NOTE: SAS Transport Files require binary mode download (see instructions below)

Binary Data

Data File (SAS UNIX) -- SAS (UNIX) program
Data File (SAS Windows) -- SAS (Windows) program
Data File (SPSS UNIX) -- SPSS (UNIX) program
Data File (SPSS Windows) -- SPSS (Windows) program
NOTE1: Data files requires binary mode download (see instructions below)
NOTE2: Data files may appear to be EMPTY in a WWWeb browser, but they are OK.
NOTE3: Similar methods are used for Packed Decimal, Positive Integer Binary and other encoding methods; see the SPSS or SAS documentation for details.

Compressed Data (once uncompressed, data files will probably be one of the types shown in the above examples)

Compressed Data File (NOTE: when downloading, change the file name to rawfree.dat.gz)

There are several different compression programs; this sample file uses gzip.

You can download this sample file to UNIX and uncompress it with the following command:

gunzip rawfree.dat.gz

You can download this sample file to a PC (Windows) or Mac and uncompress it using Winzip from http://www.winzip.com/

When unzipped, this data file is equivalent to the Raw ASCII (rectangular, free format) file in the first example above, and can be read with the SPSS or SAS programs in that example

NOTE: Unfortunately, in this age of computer software trying to be too helpful, some (most?) browsers will uncompress the data before downloading, thereby destroying this example. Please complain to your browser's WWWeb site about this.

Different browsers and FTP protocols will have different ways of specifying a binary download. Binary download means that no characters are translated (changed) in the download process. The copy is byte for byte the same as the original file, regardless of differences in platform or character sets being used. (The following suggestions does not cover all browsers or all possibilities, but it should provide hints to help you figure out the details for your particular browser.)
• if you have an explicit choice (e.g., radio button or menu item) choose "binary"
• in browsers such as Internet Explorer or Netscape, in which a simple "Save As" offers only a few specific file types such as *.html or *.txt and does not give you the "All Files (*.*)" choice
  • right-click on the link for the desired [data] file
  • select "Save Target As" or "Save Link As"
  • choose "All Files" in the "Save as type:" field
  • click Save or OK
• when in doubt, consult the "Help" of the software you're using and search the term "binary download" or "binary transfer"

Raw data refers to data values that have not been processed; they can be entered in virtually any computer, by any editor or word processing software (as long as the file is saved as "text") and can be moved from computer to computer without fear of corruption. ASCII is the standard character encoding scheme for most computers in the world. EBCDIC is the IBM mainframe standard.

A rectangular file consists of straightforward rows (observations) and columns (variables) in which each row (or group of rows) is a complete observation. A hierarchical file is one in which some records contain one type of data (e.g., Household), and other records contain other types of data (e.g., Persons). Hierarchical files require considerably more programming in order to read them, as compared with rectangular files.

Free format means that each data value is separated by some delimiter, usually a space. These are also referred to as space-delimited files. In comma-delimited files the data values are separated by commas, and in tab-delimited files, the values are separated by Tabs. Raw data stored without delimiters is referred to as fixed format or column-input data. These types of files require more detailed programming (or more involved point-and-click operations) to read them in.

All statistics packages require that raw data be "read in", or processed, before analysis is possible. System files contain data that have been processed by a statistics or database package into that package's own proprietary format. SPSS creates SPSS Save Files, SAS creates SAS data sets, and so forth. Most statistics software also provides the convenience of transport files, also known as portable files.

Data may be coded in numeric or character form which basically means "numbers" or alphabetical "characters". Some data also are coded in any of several binary formats usually to conserve space. Numeric data is typically the default; all other types of data require the use of format specifications in order to distinguish their values from true numeric values.

Most of the types of data mentioned above may be stored in compressed form, as a space-saving measure. Usually (but not always) the data must be uncompressed before reading the files into a statistics package.