Aggregation

CourseSpaces allows the instructor to choose the process that will be used to calculate a total for the grade items in a category. CourseSpaces refers to this process as an 'Aggregation Method.' It should be noted that the course itself is also considered a category and must be assigned an aggregation method. There are 3 methods of aggregation:

  • Simple weighted mean of grades (*Default)
  • Weighted mean of grades
  • Natural Grading

When a new gradebook is created, it has one category already placed in it by default. This is the overall course category and its name is the name of the course. All other sub-categories and grade items are contained within this category. If the instructor does not create any other categories, then the overall course category's aggregation method will control all of the course's calculations.

Only two aggregation types easily allow for extra credit: Sum of grades or Simple weighted mean of grades.

TIP: It is extremely important and best practice to keep the gradebook and its settings as simple as possible. It is the instructor's responsibility to set up the gradebook properly to ensure calculations are correct. An instructor should not rely on Support to resolve gradebook set-up issues once the course has started. To correct issues and problems is extremely difficult.

Simple Weighted Mean of Grades

Weights are determined by the possible points for each item. For example, a 10-point quiz would have a weight of 10, while a 100-point exam would have a weight of 100. The weight or importance of a grade item is determined by the number of possible points it is worth. Scoring low on a 10-point exam does not have an equally bad affect as scoring low on a 100-point test. With this method, if you want a grade item to be worth more, or carry more weight, simply make it worth more possible points.

This aggregation method is equivalent to Sum of Grades if the instructor sets the category range to equal the total number of points possible. The difference is that Simple Weighted Mean will show a student’s actual grade at any point of time in the semester, while Sum of Grades shows a student’s point total relative to the total possible points at the end of the semester.

For example, if a category has five grade items worth 100 points each, its range of total possible points is 500. If a student scores 100 on the first two exams, Simple Weighted Mean will show their category percent score as 100%, while Sum of Grades will show their category percent score as 40%.

Weighted mean of grades

Weighted means of grades means that each item can be assigned a different weight regardless of the number of points assigned to the item. However, the total of all items must equal 100. If you create multiple category folders (ie. Tests, Assignments) and place items within them, the same applies. By choosing Weighted means of grades at the category level, you can assign a unique weight to each item within the category. You can also choose to assign an equal weight to each item.

If an item is not assigned a weight by the instructor, it is assigned a weight of 1 by default.

Natural Grading

Natural Grading serves as a single aggregation method that can supersede sum of grades, and both weighted mean and simple weighted mean of grades. Natural Grading without custom weights corresponds to sum of grades and simple weighted mean (SWM). Natural Grading With custom weights corresponds to weighted mean of grades.

 

Natural Grading as a Sum of Grades

By default, Natural Grading produces a sum of the grades aggregation. In the example below, there are three grade items worth 100, 50, and 20 points (for a total of 170 possible points). Using natural weighting, the gradebook adds up a student’s scores on the three items and reports the total (the sum). The Weights column displays the relative weights of the items (as percentages) based on each item’s points. For example, since 100/170 = 0.588235…, the Weights column for the 100-point item displays a percentage of 58.824. If the weights are not overridden by selecting them, then they are simply for informational purposes, to inform the instructor what the relative weights of the items are.

Natural Grading as Sum of Grades

Natural Grading as a Simple Weighted Means of Grades

Natural Grading can produce simple weighted means of grades if the points (sum of Max grade items) add up to 100 (see image below). If the points do not add up to 100 (see image above), then it will act as sum of grades, where the weights are not equal to the maximum points per grade item. 

Natural Grading as Simple Weighted Means of Grade

Natural Grading as Weighted Means of Grades

Instructors can override grade items’ default weights and enter alternate weights instead, by checking the box next to any of the weights. In the example below, the 100-point item (Research Paper) is actually worth half of the total grade, so the instructor checks its box in the Weights column and enters a value of 50%, overriding the default weight with the desired value. If you use custom weights, It is best practice to adjust the weights to add up to 100 (see example below)

Natural Grading as Weighted Mean of Grades

Deciding which aggregation method to use

The grade book provides many options to maintain course grades and to provide each student with a private view of their progress in your course. The flexibility of the grade book also adds some complexity.

Find the scenario that applies most closely to your grading philosophy for a particular course.

As part of your decision process, keep in mind that only two aggregation types easily allow for extra credit: Sum of grades or Simple weighted mean of grades.

Aggregation Methods

Scenario 1

If: I know in advance what all the graded course items are, and the available points per item are in proportion to each other (bigger items are worth more points).

Then: Use Simple Weighted Mean of Grades or Natural Grading as your aggregation strategy. There is no need to establish categories.

Scenario 2

If: I know in advance what all the graded course items are, but I want some items weighted more than others (e.g., a test worth 5% and a homework assignment worth 20%).

Then: Use Weighted Mean of Grades or Natural Grading. Then, assign proportional weights to the individual items.
 
Scenario 3

If: I want the flexibility to add categories of graded course items (For example, tests category worth 60%, assignments category worth 40%).

Then: Use Weighted Mean of Grades or Natural Grading. Then, add proportional weights to the categories of items that you want.
 
Scenario 4

If: Everything in my course counts the same, regardless of what scale I use to grade it. (e.g. If every grade item is marked out of 100)

Then: Use Natural Grading.