A note on statistics packages

Many computer statistics packages exist, some of them tailored specifically for the needs of psychologists. The better-known packages exist in forms suitable for Windows and Mac. Computer software evolves rapidly, and information written now may be out of date by the time you read it. Here are some possibilities:

• 1. At the time of writing, IBM SPSS and earlier versions of SPSS have reliability facilities, as well as facilities for FA and the other statistics referred to in this book. IBM SPSS (version 26 at the time of writing) is the newest version of SPSS and probably the best choice of statistics package, certainly if available to you free of charge from your university or workplace. Although SPSS is updated annually, it is not vital to use absolutely the latest version if that is not available.
• 2. If not available via your university or workplace, SPSS and IBM SPSS can be downloaded free of charge, but you need to be aware of possible problems. For example some free versions may be out of date, some come encumbered with unwanted advertisements (or may cause worse problems), and the more respectable versions may be free for only a limited time.
• 3. If you want a respectable, free, user-friendly package with a good range of statistics on offer, MYSTAT is a free student version of SYSTAT (download from https://systatsoftware.com/downloads/download-mystat). MYSTAT has a limit of 100 variables but allows any number of cases. SYSTAT - the ‘parent’ version - is not free though is considerably cheaper than SPSS; it allows unlimited variables and offers many more statistics than MYSTAT. MYSTAT offers Cronbach’s alpha but not individual item-total correlations; with x items one would have to calculate alpha x times, after removing each item, to see which items’ removal (if any) improved alpha - a little tedious but not impossible. It offers FA and PCA with a number of options, e.g. for rotation. Analyse-it is a relatively low-price statistics package that includes the tests mentioned in this book, and others. It functions as an add-on to Excel databases, an attractive feature.
• 4. Most free packages do not generally offer reliability analysis (Cronbach’s alpha) and/or FA or PCA. Wikipedia (Free statistics packages) offers a useful guide to some free packages and links to lists of free packages. Two reputable and normally easily available programmes are Minitab and Excel; unfortunately, although they offer many of the statistics referred to in this book, they do not include reliability or factor analysis.

Appendix 5 includes instructions for using IBM SPSS to compute reliability.