45 Aggregation Methods

Within the Gradebook Setup menu, you can set your courses ‘aggregation method‘ or the way that the course grade is calculated.

The three most popular grade book aggregations are Natural, Weighted Mean, and Simple Weighted Mean of Grades. Alright – now it is time for some math!

Natural

This is the sum of all grade values, scaled by their relative weights. The Maximum grade of the category is the sum of the maximums of all aggregated items. Consider ‘A’ as the student’s grade item:

   A1 70/100, A2 20/80, A3 10/10, without forcing weights:
   A: (70 + 20 + 10)/(100 + 80 + 10) --> 100/190

Note: Natural can be easily remembered as points earned divided by the points possible. These gradebooks typically exceed 100 points possible.

What it does:

• Sums the points possible for all grade items and categories.
• Natural is the easiest gradebook if you provide Extra Credit opportunities.
• This gradebook aggregation usually adds up to over 100

When to use:

• When you want to see totally face value scores of all assignments accumulated (naturally weighted). Points Earned/Points Possible. (Is also displayed as percentages and points).

Feel free to navigate to Natural Aggregation to learn additional details.

Weighted Mean

Each grade item can be given a weight to change its importance in the overall mean. In simple terms, the category “total” will be equal to the sum of the scores in each grade item each multiplied by its grade weight, and that sum being finally divided by the sum of all weights. This is shown in the following example:

   A1: 70 out of 100 weight 10, A2: 20 out of 80 weight 5, A3: 10 out of 10 weight 3, category A: maximum grade 100
   A1 -->70/100=0.7, A2 --> 20/80=0.25, A3 -->10/10=1
   A: (0.7*10 + 0.25*5 + 1.0*3)/(10 + 5 + 3) = 0.625 --> 62.5/100 --> 62.5 (out of 100)

Note: These gradebooks are locked in at 100 points possible since it is percentage-based.

What it does:

• Each graded item is assigned a weight used to determine its relative importance to the overall grade calculation.
• The weight does not need to be the same as the possible points for an item.
• If Weight = 0, it counts as 0%
• Grades automatically adjust proportionately
• No Extra Credit; instead, you can Drop the Lowest.

When to use it:

• When your syllabus shows categories worth X% and accumulative categories = 100%
• Weights of cumulative categories must = 100%

Feel free to navigate to Weighted Mean to learn additional details.

Simple Weighted Mean

Simple weighted mean is roughly a combination of both of the other aggregation methods mentioned above. The difference from the Weighted mean is that the weight of each item is its Maximum grade. For instance, using the same assumptions of the first case:

   A1 --> 70/100, A2 --> 20/80 = 0.25 A3 --> 10/10, category max 100:
   A: (0.7*100 + 0.25*80 + 1.0*10)/(100 + 80 + 10) = 0.526 --> 52.6/100 --> 52.6 (out of 100)

When the “Simple weighted mean” aggregation strategy is used, a grade item can act as Extra credit for the category. This means that the grade item’s maximum grade will not be added to the category total’s maximum grade, but the item’s grade will. For example, if A3 is marked as extra credit in the above calculation:

   A1 --> 70/100, A2 --> 20/80 = 0.25, A3 (extra credit) 10/10, category max 100:
  A: (0.7*100 + 0.25*80 + 1.0*10)/(100 + 80) = 0.556 --> 55.6/100 --> 55.6 (out of 100)

Note: These gradebooks are locked in at 100 points possible since it is percentage-based.
Feel free to navigate to Simple Weighted Mean to learn additional details.