...
- points-based calculations : in which the ratio of an item's max points versus the total points possible for all items scored is used to establish the item's 'weight' within the gradebook
- weight-based calculations : in which the product of two assigned weights at the category and item levels is used to establish the item's 'weight' within the gradebook
Points Based Calculations
There are two cases for points based calculations, but the distinctions between the two are very slight. Whenever the 'organization' of the gradebook is set to "No Categories" or "Categories", points-based calculations will be used, independent of whether the "grade type" is set to "poe ints" or "percentages". In setting up the gradebook, an instructor must provide a maximum number of points per item, or if one is not entered, a default value of 100 will be used.
...
S = sum of all non-extra-credit points earned
E = sum of all extra-credit points earned
P = sum of all non-extra-credit points possible for scored items
% score = (S+E)/P
Of course when we include the ability of instructors to excuse an individual student from an individual item, we discover that P can vary on a student-by-student basis, as shown below:
...
As you can see, it is not possible to calculate a 'category score', or in the case of this gradebook, a course grade, for Francis... s/he has received 10 extra points, but since P is zero, we get a division by zero exception.
| Note | |||||||||||||||||||||||||||||||||||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Alternative Points-Based Extra Credit CalculationOne way that we could conceivably implement the extra credit calculation would be to revise the calculation above by introducing an additional variable Q = sum of all non-extra credit points possible for scored and unscored items We would then revise the equation as follows: % score = S/P + E/Q In this case, our example above would look like this:
The obvious disadvantage of this strategy is that instructors would not see extra credit points being awarded in the most straightforward common-sense way for students with excused items... so in Dela's case, even though she has been given 10 extra points, giving her 20 out of 20 points for the gradebook, she only receives a 60%, rather than a 100%. |