Forget to mention: This is probably related to the problems of this guy:
http://moodle.org/mod/forum/discuss.php?d=195597

The error does mean exactly what it says, but perhaps it could be clearer.

The problem is that all the questions have grade 0, so quiz.sumgrades = 0, but quiz.grade is > 0. The problem is that when we get to the end of the quiz, Moodle has to compute

$grade = $summarks * quiz.grade / quiz.sumgrades

which gives a divide by zero error. Moodle 2.2 checks for this and gives the error before starting an attempt, so the teacher discovers the problem quickly and can fix it.

Thanks for your quick reply!

Yes, this summarises roughly what we figured out ourselves so far. As already mentioned in the bug report, the main problem is that our instructors/teachers used the individual grades == 0 setting on purpose to prevent the results to appear in the gradebook. It may be a dumb question (and please appologise if this is the wrong place to ask this questions), but what would be the "official" way to get an ungraded quiz for self - evaluation in moodle >= 2.2 ?

• Grades > 0 + Hiding of Grading category / aspect in grade book (this is what we do now as a workaround)
• Set quiz - grade == 0 (no idea if that case is treated differently)
• ?

I don't know if that would mesh with the philosophy behind the quiz module, but an option for "no rating" / "no grading" like there is for example in the forum in combination with a hint towards this option in the error message would be easier to grasp (at least for our teachers, who had no idea what implication setting grades == 0 had).

Many thanks in advance & best regards
Martin

The recommended way it to set quiz->grade = 0.

You may ask: why doesn't Moodle do that automatically when all the questions have grade = 0.

The answer is about what happens if a teacher decides to re-create a quiz by removing all the old questions, and then adding a new set. In this case, it is really bad if quiz->grade gets rest to zero at the point where all the questions have been removed.

And, teachers adding and removing questions from their quiz seems to be to be a more common situation than teachers creating a quiz that is not graded at all. (Although ungraded quizzes are an important use-case. That is why they work.)

Many thanks for your explanaition, the rationale behind the behaviour makes a lot of sense. We will instruct our teachers to use that approach.

best regards
Martin

OK, I have improved the error message.

Tim, your language string edit looks good to me. I've also created a page in the docs explaining the error:
http://docs.moodle.org/en/error/quiz/cannotstartgradesmismatch

Sorry I can't review your change to mod/quiz/locallib.php but I expect it's fine.

Thanks for the review Helen.

Some hours ago...

the main moodle.git repository has been updated with latest weekly modifications. You may wish to rebase your PULL branches to simplify history and avoid any possible merge conflicts. This would also make integrator's life easier next week.

TIA and ciao

Thanks for the improvement Tim, has been integrated now.

Works perfectly on all branches.

[you wouldn't believe how long I spent looking for maximum grade on the quiz edit page - not familiar enough with quiz!]

FCT (fixed, closing, thanks). Ciao

"I feel a very unusual sensation - if it is not indigestion, I think it must be gratitude!"
~ Benjamin Disraeli