Descriptive Data Analysis
Suppose that you have the data set, sample1.sav, still displayed on your screen. If not, select SPSS Data Editor - sample1.sav from the Window menu.
The next step is to run some basic statistical analysis with the data you entered. The commands you use to perform statistical analysis are developed by simply pointing and clicking the mouse to appropriate menu options. This frees you from typing in your command lines.
However, you may paste the command selections you made to a Syntax Editor window. The command lines you paste to the Syntax Editor window may be edited and used for subsequent analysis, or saved for later use. Use the Paste pushbutton to paste your dialog box selections into a Syntax Editor window. If you don't have an open Syntax Editor window, one opens automatically the first time you paste from a dialog box. Click the Paste button only if you want to view the command lines you generated. Once you click the Paste pushbutton the dialog selections are pasted to the Syntax Editor window, and this window becomes active. To execute the pasted command lines, highlight them and click run. You can always get back to the Data Editor window by selecting sample1.sav-SPSS Data Editor from the Window menu.
Generating a New Variable
Before computing the descriptive statistics, we want to calculate the mean score from the three tests for each student. To compute the mean score:
- Select Compute... from the Transform menu. A dialog box appears
- In the box titled Target Variable type in average as the variable name you want to assign to the mean score
- Move the pointer to the box titled Numeric Expression: and type: mean (test1, test2, test3)
- Click OK
A new column titled average will be displayed in the Data Editor window with the values of the mean score for each case. The number of decimal places in a newly created variable can be tailored by selecting Edit → Options → Data → Display format for new numeric variables prior to creating new variables. This display format setting affects the formats of all new subsequent numeric variables.
To run the FREQUENCIES procedure:
- Select Descriptive Statistics from Analyze menu
- Choose Frequencies...
- A dialog box appears. Names of all the variables in the data set appear on the left side of the dialog box.
- Select the variable sex from the list. It is highlighted.
- Click the arrow button right to the selected variable.
Now the selected variable appears in a box on the right and disappears from the left box. Note that when a variable is highlighted in the left box, the arrow button is pointed right for you to complete the selection. When a variable is highlighted in the right box, the arrow button is pointed left to enable you to deselect a variable (by clicking the button) if necessary. If you need additional statistics besides the frequency count, click the Statistics... button at the bottom of the screen. When the Statistics... dialog box appears, make appropriate selections and click Continue. In this instance, we are interested only in frequency counts.
- Click OK
The output appears on the Viewer screen
Our next task is to run the DESCRIPTIVES procedure on the four continuous variables in the data set.
- Select Descriptive Statistics from the Analyze menu
- Choose Descriptives...
A dialog box appears. Names of all the numeric variables in the data set appear on the left side of the dialog box.
- Click the variable average and click the arrow button to the right of the selected variable
- Do the same thing for the variables test1 through test3
Now the selected variables appear in the box on the right and disappear from the box on the left.
The mean, standard deviation, minimum, and maximum are displayed by default. The variables are displayed, by default, in the order in which you selected them. Click Options... for other statistics and display order.
- Click OK
The following output will be displayed on the Viewer screen.
Suppose you want to obtain the above results for males and females separately. The MEANS procedure displays means, standard deviations, and group counts for dependent variables based on grouping variables. In our data set sex is the grouping variable and test1, test2, test3, and average are the dependent variables.
To run the MEANS procedure:
- Select Analyze → Compare Means → Means...
- Select test1, test2, test3, and average as the dependent variables
- Select sex as the independent variable
- Click Options...
- Select Mean, Number of cases, and Standard Deviation. Normally these options are selected by default. If any other options are selected, deselect them by clicking them
- Click Continue
- Click OK
The output will be displayed on the Viewer screen.:
There may be other situations in which you want to select a specific category of cases from a grouping variable (e.g., ethnic background, socio-economic status, education). To do so, choose Data → Select Cases... to select the cases you want and do the analysis (e.g., from the grouping variable educate, select cases without a college degree). However, make sure you reset your data if you want to include all the cases for subsequent data analysis. If not, only the selected cases will appear in subsequent analysis. To reset your data choose Data → Select Cases... → All Cases, and click OK.
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