This question is about adding extra credit. I have things **weighted** in my class as follows:

Quizzes = 25%

Exams = 75%

Total = 100%

But I wanted to add **unweighted extra credit credit** assignment too. The points earned in the unweighted extra credit assignment apply to the Total but not to the Quizzes and Exams.

Thanks!

marshall naylor,

You just repeated what you had already said without answering Kona's question about what you wanted the student with the 89% to end up with. She's unlikely to be able to provide additional help without additional information.

You cannot mix points with percents, although some people fake it by making the points add up to 100%. If you are using a gradebook with assignment categories that are weighted, then you're going to have to pick a percentage to assign to the extra credit portion.

To help you understand where Kona is coming from, let's say that you have 500 points worth of exams, 300 points worth of quizzes, and you have 20 points of extra credit. These are for illustration purposes, they probably don't match your actual points.

You've weighted the gradebook so that exams are worth 75% and quizzes are worth 25%. The weighted average is the sum of the weights times the percentages divided by the sum of the weights, but the sum of the weights is capped at 100%.

A student has 87% (435/500) on the exams and 95% (285/300) on the quizzes. Before extra credit, that gives them (75 * 0.87 + 25 * 0.95 ) / ( 75 + 25 ) = 89 / 100 = 89% for the course.

Kona's question is how does that extra 20 points of extra credit get applied? It sounds like want to give them 20 extra percentage points to their grade, so 89% + 20% = 109%. If that is the desired outcome, then here's how you can do it.

Create an extra credit group whose weight as a percentage is equal to the maximum amount of points anyone could get. Then each point counts a full percentage. If there were 30 possible extra credit points, then make the extra credit group worth 30%.However, if you do this before close to the end of the term, it's going to confuse people. In particular, if you have the extra credit before everyone has grades for quizzes and exams, then it's not considered extra credit, it's part of the regular score. So you might want to keep it at 0% until later in the semester. If a student has 90% (45/50) on quizzes and 8 bonus points out of 10 possible before a test has been taken, then including the extra credit (with a maximum of 10%) too soon would make their score is ( 25*45/50 + 10*8/10 ) / ( 25 + 10 ) = 30.5 / 35 = 87.14%. That's below the 90% they had without the extra credit. That's why I say students will get confused if you include the extra credit too soon.

How does our from above student do?

Sum of weights times scores = 75*435/500 + 25*285/300 + 30*20/30 = 109

Sum of weights = 75 + 25 + 30 = 130, but it's capped at 100

109 / 100 = 109%, which is the 89% they got plus the 20% extra credit.

To help explain Kona's confusion, what I described is still weighting the extra credit. I'm just weighting it at 100% rather than 75% or 25%. You cannot weight some things and not weight others, which is why she was seeking clarification on what you wanted to do with the student who had 89%.

If what I described above isn't what you're after, then please describe it with actual numbers so we can understand what you're wanting to accomplish.