The STACK Moodle plugin is getting an upgrade!

What is STACK?
STACK is a powerful system for creating and managing online assessments in mathematics, science, and related disciplines. It’s integrated into our Moodle platform, providing a seamless experience for creating complex, auto-graded questions.

The new version, STACK 4.4, was initially released in July 2022 and is now being implemented in our Moodle platform on Tuesday 25th July. This major update focuses on enhancing the performance and overcoming limitations of the previous systems, particularly in the Potential Response Tree (PRT) and Computer Algebra System Text (CASText) systems.

However, it’s important to note that the new version of STACK has become more stringent in terms of logic and syntax. As a result, certain questions may not function as they did before. This is due to the enhanced logic/syntax checks incorporated in the new version, aimed at improving the accuracy and consistency of STACK assessments.

We have conducted tests and identified the questions that may be affected by this change. These are listed in a report on our wiki (you need to be logged in with your UCL account to view the report). We understand that this may require adjustments to your current questions and apologise for any inconvenience this may cause.
We recommend reviewing and updating your questions as necessary to ensure they function correctly after the upgrade.

To help you navigate these changes, you can review the list of key issues that might arise and their solutions in the Release Notes.

As always, we’re here to support you during this transition. If you have any questions or need assistance, please don’t hesitate to reach out to the Digital Education team.

Thank you for your understanding and cooperation as we work to improve our Moodle platform and assessment tools.

Questions in STACK can contain randomly generated elements. A student will be given a random variant of a question generated by a pseudo-random seed.

The tutor is strongly advised to pre-generate and “deploy” variants of a question. Not pre-generating question variants Forces Moodle to generate them on the fly – for quizzes with larger numbers of participants this can cause quizzes to crash/freeze.
When a student attempts the question, they will be given a random selection from the deployed variants.

Other reasons for deploying variants of a question:

• STACK runs all the question tests on each deployed variant to establish each variant of the question is working. This aids quality control. By using question tests, it is unlikely a student will be given a random variant which does not work correctly.
• The tutor can decide if each deployed variant appears to be of equal difficulty. The tutor can easily delete variants they do not like.

Caution

• If an author does not deploy any variants (not advised!) then the student gets any random variant.
• Questions that don’t use randomisation cannot be deployed explicitly. STACK automatically detects randomisation.

How to deploy question variants

The deployment interface can be found by editing a question and clicking on question tests and deployed variants.

1. The easiest way to do so is to preview the question
   
2. Then click the Question tests & deployed variant link on the top right corner.
3. Click ‘deploy’ if not already deployed.
4. Next to Attempt to automatically deploy the following number of variants, enter the number of variants  you would like and click Go.
   (depending on the question and the question note content you may be able to deploy various amount; if possible deploy over 30)
   You can preview results and either exclude variants, or return to the quiz question settings to revise the randomisation you have used in the question.
5. Check variants as required.
6. This will show the list of currently deployed variants, and links to undeploy all or a specific variant.
7. Optionally, click ‘Run all tests on all deployed variants (slow):’ and check/undeploy any variants you don’t want to use.