fix: increase grading rounding precision to avoid incorrect grades

[Agrendalath]

Enabling the rounding in #16837 has been causing noticeable (up to 1 percentage point) differences between non-rounded subsection grades and a total grade for a course. This increases the grade precision to reduce the negative implications of double rounding.

Jira

OSPR-5819

Sandbox

https://pr27788.sandbox.opencraft.hosting/
Direct link to the progress page (you can log in as staff).

Testing instructions

1. Import this course in Studio.
2. Complete two units from there.
3. Go to the Progress page and see that the score without this PR is 35%. After this change, it should be 34%.

Explanation

This course contains two subsections graded as Homework (weight: 75%):

1. In the first subsection, users can get 2 out of 3 points (66.67%).
2. In the second one, users can get 1 out of 4 points (25%).

In the current approach, the grades of subsections are rounded. Therefore, in this case, we're getting (67% + 25%) / 2 / 4 * 3 (/ 4 * 3 is because of the weight (75%)), which gives us 34.5. This is rounded up to 35%.

This PR changes these calculations to (66.67% + 25%) / 2 / 4 * 3, which returns 34.37625, which is then rounded down to 34%.

Deadline

None.

Reviewers

• @arjunsinghy96
• edX reviewer[s] TBD

Other information

Private-ref: BB-4210
Product Review: openedx/platform-roadmap#238
Settings

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[openedx-webhooks]

Thanks for the pull request, @Agrendalath!

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[arjunsinghy96]

👍 @Agrendalath LGTM.

• I tested this: Scores are displayed with more precision on Progress page graph.
• I read through the code
• I checked for accessibility issues
• Includes documentation
• N/A I made sure any change in configuration variables is reflected in the corresponding client's configuration-secure repository.

[Agrendalath]

@natabene, this is ready for your review.

[natabene]

@Agrendalath Thank you for your contribution.

[arch-bom-gocd-alerts]

📣 💥 Heads-up: You must either rebase onto master or merge master into your branch to avoid breaking the build.

We recently removed diff-quality and introduced lint-amnesty. This means that the automated quality check that has run on your branch doesn't work the same way it will on master. If you have introduced any quality failures, they might pass on the PR but then break the build on master.

This branch has been detected to not have commit 2e33565 as an ancestor. Here's how to see for yourself:

git merge-base --is-ancestor 2e335653 agrendalath/bb-4210-increase_grading_precision && echo "You're all set" || echo "Please rebase onto master or merge master to your branch"

If you have any questions, please reach out to the Architecture team (either #edx-shared-architecture on Open edX Slack or #architecture on edX internal).

[edx-status-bot]

Your PR has finished running tests. There were no failures.

[nizarmah]

Hello @natabene, would this change require a product review or is it suitable for a core contributor review?

[natabene]

@nizarmah Let me check and get back to you asap.

[natabene]

@nizarmah Thanks for asking, we considered this and will need to do a product review first.

[Agrendalath]

@natabene, just checking on this PR.

[natabene]

Sorry, no news yet.

[ProductRyan]

Hey @Agrendalath - I'm the new 2U Product Manager working on grading. Apologies on the delay in response here.

Can you confirm my understanding of this change?

It appears that this will increase the accuracy, of the rounding that is already in place, up to 4 decimal places.

Is that correct? are there any other changes that I'm not catching?

[Agrendalath]

Hi @ProductRyan, thank you for checking. That's correct - the subsection grades calculated by the platform are inaccurate because of the double rounding. Therefore, we want to increase the rounding precision to produce correct results.

This change will not affect existing persistent grades as long as they are not re-generated. Otherwise, this can cause up to a 1 percentage point difference in the results (on a rare occasion, like the one described in the PR).

[Agrendalath]

@ProductRyan, @natabene, just a friendly reminder that this is still waiting for the product review.

[feanil]

@Agrendalath I'm going through the old PRs, do you still want to pursue this PR or should we close this for now? If you're still interested I can try to get some eyes on this that could review this for you.

[Agrendalath]

@feanil, thank you for checking. We're definitely interested in merging this. Please see my last comment in the product review thread.

[feanil]

Sounds good , thanks I'll watch the product review thread and see what I can do to help unblock that.

[feanil]

Approving since Jenna has signed off on this from the product side: openedx/platform-roadmap#238 (comment)

[Agrendalath]

Update: I'll merge this once openedx/frontend-app-learning#1397 is approved.

[edx-pipeline-bot]

2U Release Notice: This PR has been deployed to the edX staging environment in preparation for a release to production.

[edx-pipeline-bot]

2U Release Notice: This PR has been deployed to the edX production environment.

[edx-pipeline-bot]

2U Release Notice: This PR has been deployed to the edX staging environment in preparation for a release to production.

[edx-pipeline-bot]

2U Release Notice: This PR has been deployed to the edX production environment.

[edx-pipeline-bot]

2U Release Notice: This PR has been deployed to the edX staging environment in preparation for a release to production.

[edx-pipeline-bot]

2U Release Notice: This PR has been deployed to the edX production environment.

[edx-pipeline-bot]

2U Release Notice: This PR has been deployed to the edX production environment.