I've done something similar by using the "drop the lowest" setting--but I see that wouldn't work since the groups complete different numbers of quizzes.
I don't understand why you have to include the empty grades especially if each group will not complete all of the quizzes.
In this case, Lynn, it seems that Artur has to exclude the empty grades from the quizzes from the "other group" (except for Quizzes 4 & 5), yet include any missed/noncompleted quizzes for their designated group.
This question is pretty similar to the thread about excluding restricted items. In some ways, it appears to require a logical operation within the calculation, which is not possible.
As I can see no way to do this with the existing setup, I have added Tracker issue MDL-61060 to add logical functions to gradebook calculations.
Just to say the MUA have a similar kind of thing as one of their proposed projects this time around https://moodleassociation.org/mod/page/view.php?id=528
That is to say, asking for more flexibility in the gradebook for different student needs. I'm giving it some votes.
