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Sometimes you may want to add a summary statistic to a categorical variable, for example, to show the mean score in a rating question. When you do this, by default the statistic is calculated on the basis of factors associated with the categories. Alternatively, you can base the calculation on a specific numeric variable.
A factor is a constant numerical value that is assigned to a category for use in statistical calculations. Factors are used when you want to base a statistic on the categories in a categorical variable rather than on a numeric variable. This is because statistics can be calculated on numeric data only and categories are not true numeric values. (Although the IBM® SPSS® Data Collection Data Model represents the responses to categorical questions as numeric values, these are in fact identifiers or codes and are not suitable for statistical analysis.)
► In the Variables pane, select the categorical variable.
► From the menu, choose:
This opens the Edit Variable window.
► Select the item after which you want the summary statistic to appear.
► From the menu, choose:
This opens the Insert Categories dialog box.
► In the list of Available Items, select the summary statistic that you want to use. For example, select Mean or Standard Deviation.
► Choose the >> button to add it to the list of items to insert.
► If required, edit the default description and decimal places for the inserted item.
► Choose OK to close the Insert Categories dialog box.
This inserts the statistic into the list of items in the variable. By default, the statistic will be calculated based on factors assigned to the categories in the variable. To add factors:
► In the Edit Variable dialog box menu, choose
► In the Add Factors dialog box, enter a starting value and an increment, and choose OK.
Factors are assigned to each category in the variable. The order in which the categories appear in the list determines the order in which the increments are applied.
► Choose Save and Close from the toolbar.