# 12.4. Add a Content Experiment in OLX¶

You work with multiple XML files to configure a content experiment. This section steps through the files involved in a content experiment that shows different content to two different groups of learners.

## 12.4.1. Define the Content Experiment in the Sequential File¶

You reference a content experiment in the file for the subsection, or sequential, in the sequential directory. For example:

...
<vertical url_name="name for the unit that contains the A/B test" display_name="A/B Test Unit">
<split_test url_name="name of A/B test file in the split_test folder"/>
</vertical>
.....


The <split_test> element’s url_name value references the name of the content experiment file in the split_test directory.

Caution

You can only define a content experiment in a unit, or vertical, in which different collections of components are associated with different experiment groups. You cannot define a content experiment at a subsection (sequential) or section (chapter) level and have different units or subsections associated with different groups.

## 12.4.2. Define the Experiment Content in the Split Test File¶

After you define the content experiment in the sequential file, you define the course content you want to test in the file in the split_test directory. This is the file referenced in the <split_test> element in the sequential file, as shown above.

In the content experiment file, you add elements for the experiment content. For this example, you add two <vertical> elements to compare the two different sets of content.

<split_test url_name="AB_Test.xml" display_name="A/B Test" user_partition_id="0"
group_id_to_child='{"0": "i4x://path-to-course/vertical/group_a",
"1": "i4x://path-to-course/vertical/group_b"}'>
<vertical url_name="group_a" display_name="Group A">
<html>Welcome to group A.</html>
<video url_name="group_a_video"/>
</vertical>
<vertical url_name="group_b" display_name="Group B">
<html>Welcome to group B.</html>
<problem display_name="Checkboxes">
<p>A checkboxes problem presents checkbox buttons for learner input.
Learners can select more than one option presented.</p>
<choiceresponse>
<checkboxgroup label="Select the answer that matches">
<choice correct="true">correct</choice>
<choice correct="false">incorrect</choice>
<choice correct="true">correct</choice>
</checkboxgroup>
</choiceresponse>
</problem>
</vertical>
</split_test>


In this example:

• The user_partition_id value references the ID of the experiment defined in the policy.json file.

• The group_id_to_child value references the IDs of the groups defined in the policy.json file and maps the group IDs to specific content.

For example, the value for group 0, i4x://path-to- course/vertical/group_a, maps to the <vertical> element with the url_name equal to group_a. Therefore, learners in group 0 see the content in that vertical.

For information about the policy.json file, see Set Up Group Configuration for OLX Courses.