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There are several different ways to calculate weighted totals in Blackboard. The following includes examples on how Blackboard calculates weighted grades. This guide was adapted from Loyola University in Chicago.

To calculate the weighted total by item

To illustrate weighted grade calculation, the following example will be used. 

Blackboard's formula for weighted total by item:
[(Earned points on item1/total points possible for item1) X (weight of item1)]+ [(Earned points on item2/total points possible for item2) X (weight of item2)] + [(Earned points on item3/total points possible for item3) X (weight of item3)] + [(Earned points on item4/total points possible for item4) X (weight of item4)]


= ((25/30)x.20) + ((30/35)x.25) + ((40/50)x.30) + ((30/35)x.25)
= (.83x.20) + (.86\x .25) + (.80\x .30) + (.86x.25)
= .166\+ .215\+ .24\+ .215
= .846 or 84.6%

Do not use the weighted score to reproduce percentages.

To calculate the weighted total by weighing by category

If you create categories for items and weight for each category, Blackboard will not total the scores in a given category and multiple the total score of all items by the weight. Instead, Blackboard divides the weight equally to each item in the given category. To illustrate the following process, a new example will be used:

In a category in which each item is weighted equally Blackboard assigns an equal portion of the percentage weight to each item. For example, in a scheme with five quizzes at 25 total points and with a total percentage of 15%, each quiz is worth 3% of the total weighted grade.

Using the Blackboard formula here is how the Weighted Total would be calculated:


= ((5/5)x.03) + (5/5)x.03) + (5/5)x.03) + (2/5)x.03)+(3/5)x.03)+((25/30)x.20)((30/35)x.20)((40/50)x.30)((30/35)x.20)
= (.03+.03+.03+.012+.018)+.166 + .17 + .24 + .17
= .12 + .166 + .17 + .24 + .17
= .866 or 86.6%

To calculate the weighted total by weighted running total

If a student has not finished all of the available quizzes, you will need to figure a Running Weighted Total instead of a Weighted Total. So of the five quizzes, let's say the student has only completed two of them (5/5 and 2/5). The following shows how Blackboard will calculate the running weighted total:


Quiz 1 [(5/5)*(.075)]= 1*.075=.075
Quiz2[(2/5)*(.075)]=.04*.075= .03
Persuasive Essay [(25/30)*(.20/1)]= .1667
Midterm [(30/35)]*(.20/1)]= .171
Academic Research Paper [(40/50)*(.30/1)]= .24
Final Exam [(30/35)*(.20/1)]=.171
= .854 or 85.4%

There is usually a .01 percent difference between manually calculated Weighted Running Total and Blackboard calculations due to rounding methods. The Grade Center will list .9242 or 92.42% for the Running Weighted Total.

To calculate the weighted total when dropping the lowest score from a category 

If you are dropping the lowest score in a category, Blackboard will reapportion the percentage given to each item in a category. For the example, this would be one of the five quizzes with scores: 2, 3, 5, 5, 5. Dropping the score of two, the percentage for each quiz will now be 15%/4 or .038 per quiz. The total points for the category will also change because a quiz is being removed from the total score (175 to 170). 


Quiz 1 [(5/5)*(.075/4)] =1*.019=.019
Quiz 2 [(5/5)*(.075/4)] =1*.019=.019
Quiz 3 [(5/5)*(.075/4)] =1*.019=.019
Quiz 4 [(3/5)*(.075/4)]=.6*.019=.011
Persuasive Essay [(25/30)*(.20/1)]= .1667
Midterm [(30/35)\]*(.20/1)]= .171
Academic Research Paper [(40/50)*(.30/1)]= .24
Final Exam [(30/35)*(.20/1)]=.171
=.817 or 81.7%

To calculate the weighted total in categories with equally weighted items consisting of different point values 

In the previous examples, all items in the Quiz category were of the same point value. If you give different point values to quiz items withing a category but want the percentage of the items to remain equal, Blackboard will apportion the percentage of the weight with the following formula.


= ((10/10*.08) + ((5/5)*.08)+((4/5)*.08)+((9/10)*.08)+((9/10)*.08) + ((29/30)*.30) + ((27/30)*.30)
= (1*.08) + (1*.08) + (.8*.08) + (.9*.08) + (.9*.08) + (.96*.30) + (.90*.30)
= .08+.08+.064+.072+.072+.288+.27
= .854 or 85.4%

To calculate the weighted total in categories with proportionally weighted items consisting of different point values

In the previous example, percentages were distributed equally among items in a category. If you will to proportion the weight of the items, the following formula is used by Blackboard.

Example from Loyola University

Blackboard determines how much of the 30% each quiz is worth in the Quiz category by dividing the total points of the item by the total points for the category (45) and then assigning the correct proportion of the 30% of the Quiz category to each item:

5/45=x/30%; x=3.33% or .0333
10/45=x/30%; x=6.67% or .0667
15/45=x/30%; x=10.0% or .100

For Student A with exactly the same point totals as shown in Example 6, substituting these percentage values into the Blackboard formula for the Weighted Total produces the following:

= ((9/10*.0667)+((5/5)*.0333)+((4/5)*.0333)+((12/15)*.10)+((8/10)*.0667) + ((47/50)*.35) + ((88/100)*.35)
= \[(.9*.0667) + (1*.0333) + (.8*.0333) + (.8*.10) + (.8*.0667)\] + (.94*.35) + (.88*.35)
= \[.060\+ .0333\+ .02664\+ .08\+ .0534\] + .329\+ .308
= (.25344 - quiz weighted total)+.329 (essay weighted total)+.308 (final exam weighted total)
=.8903 or 89.03%


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