In order to configure an experiment using the EFG software, you will first need to create a configuration and an experiment group (or as many distinct ones as you may need). Add a configuration to the configuration group you have created, choosing EFG out of the available experiment types, and click "Add". Once it has been added, click the "Edit" icon.

At the Edit screen, click "Configure parameterization". This parameter set, which will contain all the information required to run an experiment, can then be used for different experiments, as many times as required, since it is independent of the experiments that are run.

A new window will be opened for the experiment setup. The first step in the parametrization of the experiment is to create a game tree using the tree editor, after having entered the number of players. You can even create single-player games, like a lottery-choice game, using the EFG tree editor.

You can create multiple game trees to be used for the same experiment. Simply click "Add", next to the Tree select box, and enter unique names for each game tree.

Screen Capture: Tree Editor Screen

The tree editor consists the following:

1. Grid area: This is the white area with grid lines, in which you will actually build a game tree.
2. A palette of tools, which include:
   1. Decision node tool: The green circle represents a decision node. Click the tool and then click the part of the grid area where you would like to place this decision node.
   2. Nature tool: To represent a decision node for an action to be taken by Nature, use this tool in the same manner as the decision node tool.
   3. Action tool: The line with green circles at each end denotes the action tool, which you will use to represent an action connecting two decision nodes. To create an action, click the action tool. Click on the first decision node, for the player who must take the action, and then click on the decision node for the player who must respond to this action.
   4. Payoff node tool: To create the final payoff nodes at the end of the game tree, use this tool in the same manner as the decision node tool. Connect it to the appropriate decision node using the action tool.

Double-click on each tool to edit its properties on the left-hand side of the screen.

• For decision nodes, you will need to select which player takes the decision at that node.
• For actions, you can select a label.
  If the action is one taken by Nature, you will need to enter the probability of each action being taken.
• For payoff nodes, you will need to double-click on the "Value" cell in the table on the left hand side of the screen and enter payoff values for each player.

Screen Capture: Tree Editor Screen with payoff value setup

The first decision node you place on the tree editor takes on the function of the root node, i.e. the very first decision to be taken during the game. This may be a normal decision node, or a Nature node. Each game tree must contain a root node, and a root node cannot have any actions leading to it, only from it. The root node is highlighted in yellow, instead of green like regular nodes, when it is first placed on the tree editor.

Next: Configuring a session