SPSS for Windows
A brief tutorial
This tutorial is a brief look at what SPSS for Windows is capable of doing. Examples will come from Statistical Methods for Psychology by David C. Howell. It is not our intention to teach you about statistics in this tutorial. For that you should rely on your classes in statistics and/or a good textbook. If you're a novice this tutorial should give you a feel for the programme and how to navigate through the many options. Beyond that, the SPSS Help Files should be used as a resource. Further, SPSS sells a number of very good manuals.
The Basics
SPSS for Windows has the same general look a feel of most other programmes for Windows. Virtually anything statistic that you wish to perform can be accomplished in combination with pointing and clicking on the menus and various interactive dialog boxes. You may have noted that the examples in the Howell textbook are performed/analyzed via code. That is, SPSS, like many other packages, can be accessed by programming short scripts, instead of pointing and clicking. We will not cover any programming in this tutorial.
Presumeably, SPSS is already installed on your computer. If you don't have a shortcut on your desktop go to the [Start => Programs] menu and start the package by clicking on the SPSS icon.
Before proceeding I should say a few words about a very simple convention that will be used in this tutorial. In this point and click environment one often has to navigate through many layers of menu items before encountering the required option. In the above paragraph the prescribed task was to locate the SPSS icon in the [Start] menu structure. To get to that icon, one must first click on [Start] then move the pointer to the [Programs] options, before locating the SPSS icon. This sequence of events can be conveyed by typing [Start => Programs] . That is, one must move from the outer layer of the menu structure to some inner layer in sequence....
Now, back to the tutorial.
Once you've clicked on the SPSS icon a new window will appear on the screen. The appearance is that of a standard programme for windows with a spreadsheet-like interface.
As you can see, there are a number of menu options relating to statistics, on the menu bar. There are also shortcut icons on the toolbar. These serve as quick access to often used options. Holding your mouse over one of these icons for a second or two will result in a short function description for that icon. The current display is that of an empty data sheet. Clearly, data can either be entered manually, or it can be read from an existing data file.
Browsing the file menu, below, reveals nothing too surprising - many of the options are familiar. Although, the details are specific to SPSS. For example, the [New] option is used to specify the type of window to open. The various options, under the [New] heading are,
- [Data] Default window with a blank data sheet ready for analyses
- [Syntax] One can write scripts like those present in the Howell text, instead of using the menus. See the SPSS manuals for help on this topic.
- [Output] Whenever a procedure is run, the out is directed to a separate window. One can also have multiple [Output] windows open to organize the various analyses that might be conducted. Later, these results can be saved and/or printed.
- [Script] This window provides the opportunity to write fullblown programmes, in a BASIC-like language. These programmes have access to functions that make up SPSS. With such access it is possible to write user-defined procedures - those not part of SPSS - by taking advantage of the SPSS functions. Again, this is beyond the scope of this tutorial.
Also present in the [File] menu are two separate avenues for reading data from existing files. The first is the [Open] option. Like other application packages (e.g., WordPerfect, Excel, ....) SPSS also has it's own format for saving data. In this case, the accepted extension for any file saved using the proprietary format is "sav". So, one can have a datafile saved as "data1.sav". Anyways, this format is not readable with a text editor, it is a binary format. The benefits are that all formatting changes are maintained and the file can be read faster, hence the [Open] option. It is specifically meant for files saved in the SPSS format. The second option, [Read ASCII Data], as the name suggests is to read files that are saved in ASCII format. As can be seen, there are two choices - [Freefield] and [Fixed Columns]. Clicking on one of these options will produce a dialog box. One must specify a number of parameters before a file can be read successfully.
Reading ASCII files requires that the user know something about the format of the data file. Otherwise, one is likely get stuck in the process of reading, or the result may be a costly error. The more restrictive format is [Fixed Columns]. One must know how many variables there are, whether a variable is in numeric or string format, and the first and last column of each variable. For example, think of the following as an excerpt from an ASCII datafile.
male 37 102
male 22 115
male 27 99
.... .. ...
female 48 107
female 21 103
female 28 122
...... .. ...
An examination of the datafile provides several key pieces of information,
- There are 3 variables
- Variable 1 is a string , Variable 2 and 3 are numeric
- Variable 1: first column=1, last column=6
- Notice that none of the columns overlap. The longest case for column one is the name "female", that spans from the first column to the sixth - or, the letter e. As you can see, one has to manually locate the first and last column, of each variable.
- Variable 2: first column=9, last column=10
- Variable 3: first column=12, last column=14
The [Freefield] option is less restrictive. Essentially, the columns can be ragged (i.e., overlapping). One need only preserve the order of each variable across all of the cases.
male 37 102
male 22 115
male 27 99
.... .. ...
female 48 107
female 21 103
female 28 122
...... .. ...
Experiment with creating datafiles and reading them with this method. As for the SPSS format, there are a large number of sample datafiles included in your package. Just click on [Open] and find the SPSS home directory. Make sure the filetype in the dialog box associated with [Open] is set to "*.sav" - the default...
Before we move onto actual data, click on [Statistics] . The menu that appears reveals many classes of statistics available for use. Each class is further subdivided into other options, as denoted by the little arrow at the right size of the menu selector. Explore what is offered by moving your mouse over the various procedures listed.
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