GNU PSPP — Frequently Asked Questions

Here we try to answer some of the questions about PSPP that arise from time to time.

What is PSPP?

PSPP is a program for statistical analysis of sampled data. It is a free replacement for the proprietary program, SPSS.

One goal of the PSPP project is compatibility with the SPSS language. It currently features:

What can PSPP do?

PSPP provides many transformations and utilities. Procedures provide the ability to perform t-tests, anova, linear regression, logistic regression, cluster analysis, reliability analysis, factor analysis, non parametric tests and other analyses.

Refer to the manual for the complete list of supported commands.

Where can I get PSPP?

See this page.

How do I install PSPP?

There are several methods:

How do I get started using PSPP?

Having installed PSPP, try this:

  1. Using your favourite editor, write a file (name it myfile.sps) containing the following: 
    DATA LIST LIST /name (a25) quantity (f8).
BEGIN DATA.
widgets 10345
oojars 2345
dubreys 98
thingumies 518
END DATA.
 
LIST.
 
DESCRIPTIVES /quantity
 /statistics ALL.
  2. Enter the command pspp myfile.sps
  3. Look at your results in pspp.list

PSPP is very versatile and there are lots of different types of statistical analysis possible. You need to become familiar with the documentation to unleash its full potential.

How do I configure the PSPP interface language?

PSPP respects the locale of the environment. So if, for example, your operating system (or the currently logged in user) is set to Portuguese, then that is what PSPP will display.

How you change the environment's locale depends on the operating system. For example, on GNU or on GNU/Linux you could use the command export LANG=pt_PT (for Portuguese spoken in Portugal) or export LANG=pt_BR for Brazillian Portuguese. This should also work for all operating systems which are POSIX compliant. On Windows 10, users reported success following these instructions. For others, you will have to refer to your OS documentation.

What documentation is available?

The PSPP manual, written in Texinfo format, is the primary reference for using PSPP. Besides the Texinfo format a few other formats are available like HTML and PDF. A few additional documentation files are included in the source distribution:

README
A quick introduction to PSPP.
INSTALL
Notes on building and installing.
ChangeLog
Details of the latest bleeding edge changes.

A manual for PSPP in French, written independently by Julie Séguéla, is also available in PDF and LaTeX formats.

A guide to PSPP in Polish, written independently by Daniel Mider and Aneta Marcinkowska, is also available.

There are also heaps of unofficial resources on the internet. Use a search engine to find them.

There are a lot of concepts I don't understand. Where can I learn about them?

One good online introductory statistics textbook is Online Statistics Education: A Multimedia Course of Study (http://onlinestatbook.com/). Project Leader: David M. Lane, Rice University. Disclaimer: PSPP, its developers and the GNU Project have no affiliation with this publisher or author of this book.

PSPP is a clone of SPSS. So why should I use PSPP when SPSS has all the same features?

Firstly, PSPP is not a "clone". No part of SPSS was used to write PSPP and there is no code shared between the projects. If it was a clone, then there would indeed be no advantage using one program or the other. But instead, PSPP is an independent free software program (and one of its design goals was ease of use for people already familiar with SPSS).

Among other advantages, this means that if you find it doesn't completely fit your needs - perhaps there is a statistical test which you would like it to perform - then you have the means and the right to improve it to fit your requirements. Whereas if you attempted to do this with non-free software such as SPSS it would be both difficult and illegal.

Furthermore, because PSPP is free software, you can use it for whatever you like and for as long as you like (there's no "expiry") and you are welcome to give away (or sell) copies to others - for example to students undertaking an introductory statistics course. If you have made your own improvements, then you can include those changes in the copies you distribute.

Another important advantage: Since the source code is available to all, unlimited peer review is possible. Should PSPP's accuracy be called into question, it can easily be audited by a competent, independent authority. Conversely, since the source code of proprietary software is secret, nobody can check to see if it contains numerical instability, inappropriate algorithm implementations or other potential errors.

Some secondary reasons why people sometimes prefer PSPP include:

How can I be sure that PSPP gives accurate results?

When you install PSPP, the GNU Project gives you exactly the same warranty that you would get with any proprietary program viz: None at all.

However, we feel confident that PSPP provides reliable and accurate results for a number or reasons

As already mentioned, the Free Software Foundation does not provide any warranty for PSPP. However, unlike with proprietary software, you are free to engage any third party of your choice to provide a support contract and/or a warranty service with terms acceptable to you.

Can I use PSPP at school/college/university?

Many introductory statistics courses specify the use of some statistical analysis software. Some schools specify or recommend the use of PSPP. Others will permit its use if the student asks. If you are enrolled in a course which specifies a proprietary statistical analysis program, we would encourage you to speak to the coordinator of the course and explain that you would prefer to use a free software package (such as PSPP) instead. Today, many schools and universities have a formal policy that students must not be compelled to use proprietary software when an alternative exists. It is worth finding out if this is the case at your institution. Speak to your students' association if necessary.

Are PSPP's results accepted for publication in scientific papers?

What is and is not accepted for publication in a journal is up to that journal's editor. We are not aware of any paper ever having been rejected on the grounds that PSPP was used, but we are aware of studies using PSPP for analysis, which have been published by reputable academic journals.

Please also be aware of PSPP's warranty.

I get an error message: "Number followed by garbage" and my data is blank.

This warning means that you are trying to import data using DATA LIST and the data encountered does not match the format you have specified. Check that there are no stray characters in the data.

If you are running under a non English locale and you are importing decimal data, it is likely that you have data with dots as decimal separators whereas PSPP is expecting commas. Either change the dots to commas, or place the line SET DECIMAL DOT. at the top of the file.

Results are displayed only to 2 decimal places. I need more.

At the top of your syntax file, or in your .pspprc file, put (for example) the line SET FORMAT F22.6. which will tell PSPP to print all results to 6 decimal places and to a formatted width of 22 columns.

I have my data in a spreadsheet. How can I import it into PSPP?

PSPP can directly import spreadsheets created by Gnumeric, LibreOffice and Openoffice.Org. To do so, use the GET DATA command. Alternatively, if using the GUI, click on "File|Import Data".

We recommend you convert all your spreadsheets either to Gnumeric or Libreoffice format to avoid this extra step. If you have the proprietary spreadsheet program MSExcel you can do this in one of the following ways:

Can PSPP open encrypted .sav or .sps files?

PSPP includes a tool, named pspp-convert, that can decrypt encrypted .sav or .sps files, given the password. Please read the PSPP manual or the pspp-convert manual, for details.

The SPSS encrypted syntax file format is unacceptably insecure, so to discourage its use PSPP and PSPPIRE do not directly read or write this file format.

How can I get more information on PSPP?

There are several resources for PSPP information. The first is this FAQ and related documentation in the distribution and on the web site. The second is the PSPP source code itself, if you are programmatically inclined.

For discussion with other PSPP users, comments, or questions, our mailing list pspp-users@gnu.org is available. You can subscribe to this list at http://lists.gnu.org/mailman/listinfo/pspp-users

Why don't you merge PSPP with R, GRETL, Octave ... <my favourite program>?

This suggestion comes up from time to time. It is unlikely to happen for a number of technical, philosophical and legal reasons.

However, we certainly want to provide features which will make PSPP easier to interact with other programs. If you want an import/export filter or some other feature to help PSPP complement your favourite program, then please talk to us about it.

PSPP lacks this feature which I really need. How can I get PSPP to support it?

There are several ways:

Any help you can give is appreciated. See the following question.

Can I help out with PSPP development?

Yes. We will gladly accept help in the form of improvements to the code, artwork or documentation.

When you have fixed a bug or improved some parts of PSPP, you can submit your patches at http://savannah.gnu.org/patch/?group=pspp

Sometimes users wish to contribute money toward PSPP development. The PSPP developers appreciate the spirit behind this idea, but monetary donations are less useful than other forms of help.

Something doesn't work properly on Windows/Mac.

PSPP is GNU Software and part of the GNU System. That means the platforms under which it works best are GNU and GNU/Linux. Like all GNU software, cross platform portability is something which we try to achieve, but it is not the highest priority. Furthermore, supporting free systems takes precedence over non-free platforms, such as windows or Mac OS, and as a matter of policy PSPP will always work best on a free operating system.

To sum up: Windows and Mac are low on our list of priorities. We recommend you switch to a free operating system. Bug fixes however, are always accepted.

What does PSPP stand for?

PSPP does not have any official acronymic expansion. But they're easy to come up with. For example:

Send along your favorites!

Help! I'm stuck

If you need help using or installing PSPP, and the documentation and FAQ do not help enough, please contact us through the pspp-users mailing list.