Quantile-Quantile Plots

Graphical Analytic Techniques

Ribbon bar. Select the Graphs tab. In the More group, click 2D and from the menu, select Quantile-Quantile Plots to display the Quantile-Quantile Plots Startup Panel.

Classic menus. On the Graphs - 2D Graphs submenu, select Quantile-Quantile Plots to display the Quantile-Quantile Plots Startup Panel.

This plot is useful for finding the best fitting distribution within a family of distributions. The first step therefore, is to choose which of the theoretical distributions to fit to the data. After selecting the distribution from the list in this dialog (see Advanced tab), you may or may not need to specify certain parameters for that distribution. For more information, see Assessing the Fit of a Distribution via Quantile-Quantile Plots.

The Quantile-Quantile Plots Startup Panel contains six tabs: Quick, Advanced, Appearance, Categorized, Options 1, and Options 2. The following options are available regardless of which tab is selected.

OK. Click the OK button to produce the graph.

Cancel. Click the Cancel button to close the Startup Panel without creating a graph.

Options. See Options Menu for descriptions of the commands on this menu.

By Group. Click the By Group button to display the By Group specification dialog box.

Sel Cond. Click the Sel Cond button to display the Analysis/Graph Case Selection Conditions dialog box, which is used to create conditions for which cases will be included (or excluded) in the current analysis. More information is available in the case selection conditions overview and syntax summary.

Case Weights. Click the Case Weights button to display the Analysis/Graph Case Weights dialog box, which is used to adjust the contribution of individual cases to the outcome of the current analysis by "weighting" those cases in proportion to the values of a selected variable.

Graphs Gallery. Click the Graphs Gallery button to display the Statistica Graphs Gallery dialog box, which is used to easily switch among different types of graphs.

Updating. Click the Updating button to display the following menu commands:

Auto. Select Auto to disconnect the graph from the graph creation dialog box and connect the graph directly to the spreadsheet. Any changes in the spreadsheet data (including selection condition changes) will be immediately reflected in the graph.

Manual. Select Manual to disconnect the graph from the graph creation dialog box and connect the graph directly to the spreadsheet. Any changes in the spreadsheet data will be reflected in the graph only after a manual update is initiated.

Locked. Select Locked to disconnect the graph from the graph creation dialog box and connect the graph directly to the spreadsheet. The graph is linked to the spreadsheet, but will not be updated when the spreadsheet data changes.  

Analysis. Select Analysis to connect the graph to the graph creation dialog box and disconnect the graph from the spreadsheet. Changes to analysis options (such as fit type) will be applied to all graphs created by the analysis.

Analysis/Updating. Select Analysis/Updating to connect the graph to the graph creation dialog box and disconnect the graph from the spreadsheet. The analysis (while open) will update the graph when the spreadsheet data is changed. Once the analysis is closed, the graph will no longer update when the spreadsheet data is changed.

None. Select None to disconnect the graph from both the spreadsheet and graph creation dialog box.

See also, Conceptual Overviews - Quantile-Quantile Plots.