[#12547] Empty weights for MCQ

[peasantbird]

Fixes #12547

Outline of Solution

1. Allow weights to be null in validateQuestionDetails()
2. Update tooltip for "Options are weighted" checkbox
3. Show '-' for weighted percentages for options with empty weights
4. Update headers in per recipient statistics to show empty weights (denoted by Option[-])
5. Calculate correct total and average scores (skip over empty weights)
6. Show '-' for total and average when all options have empty weights

Screenshots

MCQ with empty weights can be saved:

MSQ with empty weights can be saved:

MCQ Feedback session results:

When all weights are empty:

With one or more non-empty weights:

MSQ Feedback session results:

When all weights are empty:

With one or more non-empty weights:

[github-actions]

Hi @peasantbird, thank you for your interest in contributing to TEAMMATES!
However, your PR does not appear to follow our contribution guidelines:

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[jasonqiu212]

Sorry this review took so long.. You're PR is on the right track! Some observations:

1. Users cannot give the "other" option an empty weight. System will always change it to 0.

Screen.Recording.2025-03-24.at.4.04.58.PM.mov

2. In the below image, for the column titles for Per Recipient Statistics, let's add a space between the option label and assigned weight for readability. For instance, "option 1 [-]".

3. Also would it be possible to add a tooltip icon behind "Per Recipient Statistics" to indicate the format used for "Option 1 [-]"? Similar to this:

3. When I download the results, the display of the null values should be handled too (i.e., display using "-"). You can refer to [#12544] Rubric Question Statistics: Handle empty weights #12545 and see how I modified src/web/app/components/question-types/question-statistics/rubric-question-statistics.component.ts to fix this similar problem

[jasonqiu212]

This code is correct! but I was just initially puzzled by how we can set weight to be null when it's of number type. Turns out we can.. by doing const weight: number = null as any; to bypass the type checking, and i think that's what we're doing here.

I think we should follow TypeScript's type safety as best as we can for both type safety and readability. Thus, I think we need to change the following:

Line 17: weightPerOption: Record<string, number | null> = {};
Line 18: weightedPercentagePerOption: Record<string, number | null> = {};
Line 48: const weight: number | null = this.question.mcqWeights[i];
Line 57: const weight: number | null = this.weightPerOption[answer];
Line 58: Add a null check, similar to what you did here
Line 63: const weight: number | null = this.weightPerOption[answer];
... probably many more, please add as you see fit

[jasonqiu212]

I realized I did not do this in #12545 and set a bad example 🙏