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Building an example-tracing tutor for fraction addition

Last updated July 20, 2011

Table of Contents

Note: You can follow this tutorial with either the Flash or Java version of fraction addition included with CTAT.

Prerequisites:

  • CTAT 2.0+
  • For Flash version of fraction addition:
    • Flash Player 10+
    • Student interface:
      {CTAT}\Projects\FlashFractionAddition\fractionAddition-mx.swf
  • For Java version of fraction addition:
    • Student interface:
      {CTAT}\Projects\FractionAdditionTutor\FractionAddition.class

1. Introduction

In this tutorial, you will use a completed student interface and CTAT's Behavior Recorder to author an Example-tracing Tutor for the fraction addition problem 1/4 + 1/6. You will author the tutor by demonstration, without programming.

An Example-tracing Tutor is primarily composed of a student interface (CTAT supports Java and Flash student interfaces created with our tools) and a Behavior Recorder graph (BRD file) that stores data on the current problem. Multiple BRDs (problems) are often used with a single student interface.

When authoring an Example-tracing Tutor, both the student interface and CTAT must be running, as they communicate with one another during the authoring process.

2. Run the student interface and CTAT

The first step in authoring an Example-tracing tutor is to open both the student interface and CTAT. For this, you have a choice between Java and Flash student interfaces: run either CTAT for Java or CTAT for Flash.

To open a Flash student interface for fraction addition:

  1. Open a web browser, and drag the fraction addition interface SWF listed above onto the browser window. (Alternatively, if you have the Flash IDE, you can use it to open the SWF.)
  2. Launch CTAT for Flash.
  3. Position the CTAT window and Flash student interface so that both windows are visible (see below).

Note: If Flash presents a security warning, load the Global Security Settings panel, and add the location localhost to the list of allowed locations. This will enable the Flash student interface to communicate with CTAT. For detailed instructions, see Adobe's Flash Player TechNote.

Launching both the Flash student interface and the Behavior Recorder for Flash

Figure 1. Positioning the Flash student interface for fraction addition and 'CTAT for Flash' side-by-side.

To open a Java student interface for fraction addition:

  1. Launch CTAT for Java.
  2. Select File > Open Student Interface. Locate and open the fraction addition interface CLASS file
    {CTAT}\Projects\FractionAdditionTutor\FractionAddition.class.
  3. Position CTAT and the Java fraction addition interface so that both windows are visible (see Figure 2 below).

Launching both the Java student interface and the Behavior Recorder

Figure 2. Positioning the Java student interface for fraction addition and 'CTAT for Java' side-by-side.

3. Create a start state

Once your interface is running and connected to the Behavior Recorder, the next step is to create the initial problem state, or "start state". In your student interface, enter the two fractions 1/4 and 1/6 in the Given Fractions column.

To make this state the start state for the given problem, select Graph > Create Start State in the Behavior Recorder. When prompted for a start state name, enter 1-4+1-6, and click OK. You should now see your start state in the Behavior Recorder as a new node titled "1-4+1-6".

Graph start state

4. Demonstrate Solutions

After creating a start state, demonstrate correct and alternate answers, as well as common errors, that students might make for this problem. The Behavior Recorder will record the demonstrated behavior in the form of a "behavior graph".

Ensure that CTAT's Author Mode is set to Demonstrate (see below). Then demonstrate a correct solution to the problem. The Behavior Recorder records each demonstrated step as a 'link'—the line connecting two nodes—in its graph. In the graph, actions are represented by links, while states are represented by nodes.

Author Mode is set to Demonstrate.

One solution path demonstrated.

You can demonstrate an alternative solution path—one which is correct but not preferred—by clicking on the start state node in the behavior graph, and demonstrating the solution steps for that path. For 1/4 +1/6, you might demonstrate a solution where the student multiplies the denominators to get a common denominator of 24. This solution is valid, but not preferred, as '24' is not the least common denominator. Preferred paths in the graph show thick lines for edges, while unpreferred paths show a thin line.

An alternate solution path demonstrated.

If you forget to include a solution step, click on the node that precedes that step (you'll see the student interface update to reflect the state of that node), then demonstrate your step.

Tip: It is good practice to include a Done action at the end of each path in your behavior graph for two reasons: first, it is part of a cognitive skill to know when a problem is solved; second, when you create a curriculum consisting of a series of problems, the Done action, when accepted by the tutor, is a signal to present the next problem.

5. Annotate solution steps

5.1 Incorrect steps

Now you will demonstrate an incorrect step in the problem, so that the tutor will be able to recognize this error when it is performed by students. In general, any student input that is not recognized by the tutor is marked as incorrect; but by defining incorrect steps in the graph, the tutor will be able to provide a customized error feedback message for the specified input.

For the current simple problem, we will focus on the error (presumed to be common by students who have not yet mastered fraction addition) of adding the two denominators of dissimilar fractions without converting them. For the current problem, they would enter 10 as either of the converted denominators, or the answer denominator, rather than a common denominator such as 12 or 24.

In the Behavior Recorder, first click on the start state; this will reset the interface to the start state. Next, type 10 in either of the fields for the denominator of the converted fraction. You should see a new link and state appear in the Behavior Graph.

By default, the Behavior Recorder assumes that any demonstrated solution step represents a correct step. When demonstrating incorrect actions, you therefore need to mark them explicitly as incorrect behavior. So right-click the edge that was created for an input of 10 and select Change Action Type > Incorrect Action (Bug) (see below). At the prompt to edit the error message, enter an error message that the student will see when they perform this action.

You can repeat this process for any incorrect action. Note that when a student performs an incorrect action, the student will not advance past the incorrect link.

Setting an incorrect action.

5.2 Hint messages

You can attach hints to the links that represent correct actions. These hints will be displayed when the student requests a hint. Typically, multiple levels of hints are available for each action.

To define a hint message, click on a green action label displayed on an edge. From the pop-up context menu, select Edit Hint and Success Messages. Here you can define hints that will be shown to the student when they request a hint.

Editing hints for link

5.3 Skill labels

In this step you will add skill names (also known as production rule names or knowledge component labels) to the links in the behavior graph. The skill names correspond to the skills the student needs to perform in order to complete the problem. Later, if you create production rules for your tutor, you will create production rules that correspond to each skill name. When creating an Example-Tracing tutor, you do not need production rules, but the skill names will also be used for knowledge tracing.

To view and edit skills, you need to turn on the skill name display. This allows you to view the skill labels for each link. To do so, select Graph > Show Skill Labels from the CTAT menu. You should see some labels with "unnamed" appear on the graph. These labels are the skill names.

To edit a skill name for an edge, right-click the skill name label for that edge and select Edit Skill Name. A dialog box titled "Edit skill name 'unnamed'" will appear.

The skill context menu

In the Edit Skill Name box, enter a name for your skill. Subsequent skill name dialogs will allow you to choose from a list of existing skills that you have defined. The "Skill set" field refers to the category of the skill, such as "fraction addition".

5.4 Save your changes

Select File > Save Graph (or use the keyboard shortcut Ctrl-S or Cmd-S) to save the behavior graph.

6. Test your tutor

You can now test the tutor you have created. Set CTAT's Author Mode to Test Tutor (see Figure 8).

To test your tutor from the beginning, click the start state in the behavior graph; then interact with the student interface.

To test from any other step in the problem, click the desired state in the behavior graph—the student interface will update to reflect the problem-solving state—and then interact with the student interface.

Figure 8: Setting Author Mode to Test Tutor.

You can switch between Demonstrate and Test Tutor modes while authoring to iteratively test and refine your tutor.