Case Weights

The clickable Weight: Off (or Weight: On) field of the status bar displays the current status of the Spreadsheet Case Weight option. That is, an option to treat values of a selected variable as (integer) case multipliers when processing data or fractional weights, if applicable (for example, fractional weights are supported in Basic Statistics and Tables, Multiple Regression, Variance Components, Correspondence Analysis, GLM, GLZ, GRM, PLS, GDA, and specialized scatterplots). The weights can be used either for analytic purposes (e.g., some observations can be measurably more "important" and this importance can be represented by weight scores) or to economize data storage (e.g., in some large datafiles, such as a census or survey data, many cases can be identical and can be represented by one case with an appropriate case weight attached to it).

The Weight: Off (or Weight: On) field also acts as a button: Click the Weight: Off field to display the Spreadsheet Case Weights dialog, which shows the weight variable (if one was defined). This is only available if the current input spreadsheet is selected. Note that case weights can also be displayed by clicking the Define Weight button or by using the Tools menu.

Note that unless you are at the beginning of an analysis or graph, a warning message is displayed asking if you want to start a new analysis or graph because changing case weights in the middle of an analysis or graph can lead to inconsistent results (i.e., different stages of computations would be based on different configurations of data). However, if you click this status bar field at any point when the conditions can be adjusted (e.g., before an analysis is started), the Spreadsheet Case Weights dialog is displayed allowing you to specify a weighting variable.

Note that case weights can also be specified for only the current analysis or graph (and hence not be tied to the current datafile) by clicking the button to display the Analysis/Graph Case Weights dialog. This button is included on all Startup Panels and all analysis or graph definition dialogs that are displayed before the data processing begins.