I found, after grading an assignment, that it was more difficult than I intended, so I'd like to reduce the weight of the assignment. I gave letter grades for the assignment, so I should be able to change the weight freely, right?
Wrong! If I reduce the weight of the assignment, it changes all the grades to A, because it doesn't actually remember what I entered, only some bogus number of points that it assigned, and if I change the weight of the assignment, it thinks everyone did great!
So how do I change the weight of an assignment after grading it? I don't want to move it out of the assignment group it is in, because that would screw up the weighting of the different groups. (I've got already got four different groups of assignments, each with 5–12 assignments in it.)
By changing the "weight" of the assignment, do you mean changing the point value (making it worth 50 points instead of 100 for example) or do you mean something more complex? The term "weight" is normally associated with assignment groups, but the weight an assignment receives within that assignment group is based on the points associated with that assignment. I just want to make sure we're talking about the same thing so the solutions people provide are targeting the right thing.
If you mean changing the point value of the assignment, then here's my initial thoughts.
Depending on the size of your class, it may be easiest to re-enter the grades -- as a number -- into the gradebook.
If you have a large class and are comfortable with spreadsheets, I would export the current gradebook, open it in Excel, adjust the values there (they come through with the number of points, not a letter), and then re-import the gradebook from Excel into Canvas.
With either of those two suggestions, you could scale the number of points to match the new possible points or you could curve the existing scores to match the original point value.
As a suggestion for less frustrating future experiences: By entering numbers instead of letters, you get the letter grade you're happy with without the problem of Canvas assigning the highest grade (rather than the median score) possible when you enter a letter. Many people have given up entering letter grades for just that reason -- one person explained the issue well when he showed that 4 B's + 1 A came out to be an A (89+89+89+89+100)/5=91.2 when you use the letters to enter grades.
I always enter numbers but let Canvas show a grading scale so the student sees a letter. I don't normally enter the letters directly, but I use a rubric so that I pick the appropriate grade as a category and it puts in the score that I want the students to get rather than the highest one.
If you're interested in additional light reading or perhaps venting your frustration with the current system, there are several feature ideas related to letter grades
There is another discussion that explains how they are calculated: How are points calculated for a grade entered by grading scheme?
Yes, I meant changing the points.
Perhaps it would be better if I had known from the start that Canvas doesn't support letter grades in a reasonable way. That way I could have redesigned my course to use only points—though it seems really backwards to design a course around gradebook software rather than making gradebook software flexible enough to support a grading scheme.
It is also disturbing to hear that Canvas does stupid averaging with letter grades, and does not apparently support instructors setting their own conversion of letter grades to numeric scores for averaging.
I'm still trying to decide whether I'll ever use Canvas again after this quarter. So far it has been a very awkward experience, and much slower and less reliable than grading on paper and keeping my own gradebook.
There are no correct answers here, other than that Canvas lacks reasonable functionality for anything other than accumulating total number of points. There should be a warning that entering letter grades is a really bad idea, since Canvas doesn't even remember them---just an arbitrary conversion to points that it chooses.