Sticky Notes - I don't do this for every question on the quiz. I'm going to pair the kids up and give them time to find any disagreements between their work. Often I bank on those disagreements coming up on their own. I'll write a question on a sticky note if I think kids should spend more time thinking about some problem, and I'm worried that they'll just fly through the question on their own.
In this case, I was worried that they didn't spend time thinking about a careful proof or explanation, so I wanted to slow students down and encourage them to work more on a proof.
Their Answers, Collected And Mirrored Back - For this volume question, I couldn't think of a great question to ask on a note, and I'm worried that they will only consider the answers their partners have and end up missing out some of the subtleties of their answers. Since their work was all over the place, I decided to pool all their answers and mirror them back.
Nothing - If there's a baseline of good thinking about a problem in the quiz responses, and there's just a few mistakes then I'll either write a sticky note or do nothing. I'll do nothing for a few reasons: (1) I often don't have enough time to write feedback on every question for every kid and (2) if there's a strong baseline of correct answers in class, then I can be fairly confident that important disagreements will come out when the kids are reviewing questions. Sometimes I'll scribble down a note to myself to make sure that a student has had a certain conversation with either me or her partner.
Whole-Class Questions - My kids have such a tough time using similar triangles in problems. Only one kid in my class was able to pull this question off with any confidence.
Instead of going around to groups and pushing them to catalog the sort of relationships between triangles that they might be seeing here, I'm going to do that with the entire class. Then I'm going to encourage them to separate the potentially similar triangles from the main diagram, and then I'll give them time to try this problem on their own.
So I'm using a variety of feedback and all of it is directed towards giving my kids more time and support to problem solve. This is fundamentally different from the sort of feedback that most folks give, which is directed towards reflection in preparation for future problem solving.
(Related post: Questions Are The Best Feedback)