Is X d-Separated from Y by Z?:

Applet developed by Frank Wimberly. Send comments to

Below you see a region with a number of buttons at the top. This region contains a Java applet for entering a digraph and testing d-separation questions. After you read the instructions scroll down to the point where the buttons are at the top of the screen. To use the applet do the following:

  • Click on "Add Vertices". Then select vertex locations with the mouse.
  • Click on "Add Edges". Then drag the mouse from one vertex to another to add an edge between the two.
  • When you are satisfied with the graph click the "Store Graph" button.
  • Click on the "Select X" button and then click on a vertex in the graph you have drawn. It will change color. Do the same to select the second vertex with "Select Y".
  • To identify the conditioning set: click on the "Add to cond set" button and then click on the vertices you like. X and Y cannot be in the conditioning set. Similarly for "Del from cond set".
  • Click on the "X d-Sep Y?" button to ask whether the X and Y vertices you selected are d-separated given the conditioning set you selected and the graph you have drawn. The answer will be displayed below the graph.
    Note: If you would like to enter a new graph, including vertices and edges, merely push the "reload" button on your browser.