Jonathan,
Moodle has an automatic regrade option in the quiz. There are two levels "Dry run" and "Regrade all" so you can check you're happy before you regrade. Just check the quiz is setup to use the latest version of the question to pick up any changes.
Why don't you copy the question first to a duplicate in your question bank to decide what to do and test it? Then make sure you're confident before you then modify the question in your live quiz.
As a first guess, I'd probably have two nodes in the PRT.
ATAlgEquiv({ans1,ans2,ans3,ans4},{0}); /* Checks all answers ans1,...,ans4 are 0. */
ATAlgEquiv({ans1,ans2,ans3,ans4},{1}); /* Checks all answers ans1,...,ans4 are 1. */
If you need to give individual feedback about each answer then you can have 8 nodes, e.g.
ATAlgEquiv(ans1,0);
will check ans1 is equivalent to 0.
You may not want algebraic equivalence, but if you need a stricter test then other options are documented here: https://docs.stack-assessment.org/en/Authoring/Answer_Tests/Equivalence/
I hope this makes sense,
Chris
Chris, thanks for your answer. I know about the regrade option, which I have used often. Great feature. That is an interesting answer, which I did not know you could do. I guess this would be the PRT associated with ans4. What would you do with the other PRTs?