Note: this documentation was based on the gradebook in Blackboard 5.5. In June 2003, we had Testing Services evaluate the gradebook in Blackboard 6.09. They concluded that the problems inherent the old system still exist.
As we discussed earlier, there appear to be some problems with Blackboard’s Exam Weighting function. Listed below are some observations.
Ideally when weighting test scores, one should first standardize the test scores (scale both sets of exam scores so they have the same variance) and then multiply each standardized test score by the weight (e.g. 70% for Test 1 and 30% for Test 2). Although this is the “correct” way to weight test scores, this is rarely done in practice. Most Faculty Members choose to skip standardizing and merely multiply each test score by the weight. The latter weighting procedure appears to be what Blackboard is attempting.
To refresh my memory of the problems involved with weighting in Blackboard, I created a mock gradebook containing two test scores. I then weighted Test 1 (80 point maximum) at 30% and Test 2 (100 point maximum) at 70% and exported this data to an Excel Spreadsheet. Included below is the information that was exported. The shaded area contains information exported by Blackboard, the non-shaded area contains my own calculations.
As you can see, Blackboard exported Examinee, Test 1, Test 2, Total Points, and Total Weighted Score (Columns 1 through 5). Strangely, the Total Weighted Score (Column 5) was not displayed on the Spreadsheet view of the Gradebook. Stranger still, Blackboard did not export the Weighted Percentage which was displayed on the Spreadsheet view of the Gradebook. I included this column for comparison purposes (Column 6). Columns 7 through 10 contain my calculations of the Weighted Test 1 Score, Weighted Test 2 Score, the Sum of the Weighted Test Scores, and the Weighted Percentage, respectively. The Weighted Test Scores were computed by multiplying each test score by it’s weight. As you can see, the Total Weighted Score computed by Blackboard (Column 5) matches my calculation (Column 9 - Sum of the Weighted Test Scores). However, the Weighted Percentage provided by Blackboard (Column 6) does not match my calculation (Column 10). This disparity is consistent, regardless of the weights used.
I did discover the following information regarding Gradebook Weights in the Blackboard Help:
Warning: The Adjust Gradebook Weights page lists the points possible for each item [e.g. exam grade]– the weighting formula assumes that each item has the same points possible. If items have different points possible, for example a quiz may have 20 points possible and a test may have 100 points possible, weighting them will not give an accurate measure of student performance.
Sure enough, when both exams were adjusted to have the same points possible, my calculations matched those of Blackboard.
I am not sure why Blackboard cannot accommodate weighting exams with different point totals. Indeed, because Blackboard computes the correct Weighted Total Score (Column 5), it should be no problem to compute the weighted total points possible for computing the correct percentage (in the above example, the weighted total is 94 points). It seems an incredible lack of foresight not to consider that Faculty Members would have assignments, quizzes, and exams with different total points.
Find more answers...
Are you looking for more information related to the Blackboard Gradebook? Review the answers to frequently asked questions regarding the Gradebook tool in Blackboard. Also, consider attending one of the upcoming Blackboard workshops.
Last Updated: 09/05/2007