If you have accidentally published a quiz that needs to be corrected, you can use quiz regrade to edit existing quiz questions and have Canvas recalculate student grades.
Note: The regrade function currently works only with the following question types: true/false, multiple choice and multiple answer.
View the Canvas guide for full instructions related to the regrade feature.
If you need to adjust points for a quiz that uses questions types not covered by the regrade function, you can use the "fudge points" feature in the SpeedGrader.