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Frequencies
One of the most useful functions in SPSS for becoming familiar with your data is Frequencies. It is here where you will find common elements of descriptive statistics: frequency counts; measures of central tendency (mean, median, and mode); and measures of variability (range, standard deviation, standard error). It is highly recommended to run frequencies on all variables in any data set you are working with for the first time. Examine the output carefully, keeping an eye open for unusual (out of range) values.
Open your data set. Go to the Analyze pulldown menu and select Descriptives, then Frequencies. (Note: Sequences of command such as this will be presented in abbreviated form. For example, the just described sequence would be written thus: Analyze --> Descriptives --> Frequencies.) A dialog box appears. You'll see in the text box to the left a list of all variables contained in the data set. You can choose as many or as few variables as you wish, although initially it is suggested to review all of them. Position the cursor over the variable(s) you wish to examine, left click to highlight it, then press the direction button to the right of the variable list. The highlighted variable now moves from the list on the left into the "Variable(s)" box on the right. (If you select a variable in error, remove it by performing the same procedure: position the cursor over the variable you moved by mistake, left click to highligh it, and press the direction button, and the highlighted variable returns to the original list.)
| Go now to SPSS and determine at least two variables on which to run Frequencies and move them as described above. |
Once you have determined which variables you wish to examine, click on the Statistics button at the bottom of the dialog box. Here you see the options available to you in this function. It is suggested that for an initial, get-to-know-the-data review that you choose from the Central Tendency list Mean, Median, and Mode; and from the Dispersion (or variance) list Standard Deviation, Variance, Range, Minimum, and Maximum. Click on the Continue button, and then the OK button.
| Welcome to the Output Editor in SPSS Viewer! All statistical procedures you run will appear here. The raw data have not been lost. You can return to it in Data View in one of three ways: (1) if you see two button bars along the bottom of your computer screen, one labeled SPSS Data Editor and one labeled SPSS Viewer, hit the one labeled SPSS Data Editor; (2) Window --> Data Editor; or (3) hit the grid icon on the toolbar. |
| Notice that the Viewer screen is divided into two parts. On the left you'll find a "map" of all the analyses you have run. Although perhaps not necessary at the moment, when doing numerous analyses with a large data set this map can come in handy. Click on any word and return to the results associated with it. The right hand portion of the Viewer contains the results of a given procedure. |
Look carefully at the results of your frequency analysis. It contains much useful information that enables you to answer several important questions about your data set: How many total cases (or subjects) are there in the data set? How many missing cases, if any? Do all data points fall within the range of values? Do the reported mean, median, and mode values make sense? Does the standard deviation seem plausible? What is the frequency distribution of the data (in other words, how often does a given value appear?). Knowing the answers to these questions can aid you in later analysis.
| An important reminder about Help: SPSS has an extensive help function. In each function dialog box you'll see a Help button. Accessing the Help function in any dialog box will provide descriptions and explanations of the functions of that dialog box. There is an additional Help option in the Output Editor. Click anywhere in table about which you have questions, right click, and select Results Coach. |
Charts and graphs are another, more visual way for you to inspect your data set. Notice the Charts button in the Frequencies dialog box. Play around with that option now if you wish. Module V, Displaying Data, will contain more information on graphing and charting (not yet available here).
If you haven't risked running Frequencies on all the variables contained in your data set, do so now. Be creative and explore the whole range of possibilities within this important function.
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