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Weighted grades not calculated correctly

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jpaliatka Posted: 6 Dec 2006 12:00 AM
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Hello! I am new to Dr. C and I hope someone can help. I am using Blackboard 7.1.391. I have a list of 5 items for the semester and have assigned a different weight to each Item (not by Category). I have entered grades for all Items. The Total (represented by percent) column in my grade book is not calculating the correct weighted total. It is displaying the total points earned divided by total points possible but it is not accounting for the weights that I have assigned to each item.

Sound familiar to anyone or does anyone know a solution short of hand calculating all the grades? Thanks in advance!
Jen Paliatka
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Jen,

In the gradebook, you should be seeing both a "Total" column and at "Weighted Total" column. The "Total" column will do just what you see--give a simple tally of overall points. However, you should also see the "Weighted Total" column giving the correct overall weighted total, based on the item weights you've assigned. Are you not seeing that column?

Mike
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Yes, I see the "weighted total" column. However it was set to letter grade -- I think that was throwing me off completely. I now have it set to percentage instead of letter grade and it is displaying a different percentage. But under the "View Item Detail under the weighted total column, it displays 100 points possible. My total course grades are only worth 28 points possible. Is that going to throw anything off? I don't see how to change it.

Thank you for your quick and speedy response.
Jen
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Hi Jennifer,

I think maybe you are looking at the "Weighted" points possible which will be different then the actual points awarded because of the way the weighted calculation works.

Hopefully that helps,
Eric
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I'm in the exact same situation as Ms. Paliatka - new to Dr. C, same Blackboard version, same problem. As long as I was entering homework grades, everything matched up with my Excel version of my grades, but as soon as I entered a test grade, Blackboard's calculations were off - usually, but not always, the Weighted Total was lower than the actual grade average. The amount varied as well, from less than a percentage point difference to ten or more percentage points. I have double-checked both my Excel formulas and my Blackboard weightings, and they are simple - homework average 60, test average 40. I also have Weighted Total set to calculate only grades that are entered. Even now at the end of the semester, after all grades have been entered, the averages still do not match. Due to previous calculation error issues with Blackboard, I always keep a separate set of grades in Excel. I reported the problem to our techmeisters months ago, who in turn reported it to Blackboard tech support, but our folks have heard nothing back. FWIW, they are installing SP1 today; I asked them if SP1 addresses the calculation problem, but they indicate that there is no mention of that issue. This really feels like a bug.
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This kind of thing is a little difficult to evaluate in the abstract, unfortunately, and sometimes in the past I've found that Blackboard was doing the weighting calculations correctly according to the way it utilized "weighting" but it was not the way the instructors would have done it. Would it be possible (without violating student confidentiality) to give a specific example of the numbers from your Excel spreadsheet, so we can see exactly what Blackboard is doing?

On factor that seems to come into play with category weighting is whether or not each of the items in the category has the same possible points. Is that the case for your gradebook?

Mike
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Can you be more specific in what numbers you would like to see? In the course with the 60/40 weighting, the individual homework assignments vary in their point values, but are entered in Excel as, for instance, "=12/14", i.e., the student earned 12 out of the possible 14 points. This is then formatted as a percentage in my Excel gradebook. In a separate cell, I average all the resulting percentage homework scores together using the Excel AVERAGE function. Similarly, for exams, each section of an exam has a possible number of points, which I score using the same method I would on homework items. I then use the AVERAGE function to average each separate section together for the exam's overall score, i.e., each section of the exam carries equal weight. In a separate cell, I then use the AVERAGE function to average together the overall score for each exam. Finally, in yet another cell, I multiply the homework average by .6 and add to it the exam average multiplied by .4 to get the student's overall percentage score for the course. In the previous version of Blackboard, this same formula matched what Blackboard calculated with grade weighting set to 60 for homework and 40 for exams. If you need specific student numbers, I could send you an Excel file, though FWIW, our tech support "froze" this class's grades at one point in the semester as a separate course for Blackboard tech support to examine and gave them access to the course.
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Thank you for the added detail. The "=12/14" part is some of what I was hoping to see. Still, my basic idea was just to get a sample set of grades for one of the problem students and run the calculations manually a couple different ways to see how that compares to what Blackboard was giving you, and also maybe to input them on my BB system and see if I end up getting the same results.

Just curious--how is your weighting set up up in Blackboard for the exams, if you're weighting each section of the exam individually in Excel?

Mike
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How should I send the grades to you? Is there an email address I should send them to?

In Blackboard, I just have Exams as 40 weighting, so all the exam grades I enter carry the same weight. In Excel, each section of each exam carries the same weight, so I just use the Excel AVERAGE function to average the percentage score of each individual section in order to come up with the percentage score for the entire exam. Then each of the exam scores themselves are averaged in the same manner to come up with the overall exam average. FWIW, all of the exams in this particular class are paper exams. I enter the score for each section in Excel to come up with the overall score for that exam (to two decimal points), then enter that percentage score in Blackboard, with each exam being set up to be worth 100 points, so that whether I were to show the Blackboard score as a score or as a percentage, it ends up being the same number and calculates the same.
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When I asked for examples, it was just to see if you could post some representative grades and results here since Dr C's is intended to be a public question and answer forum, but that's why I mentioned the question of student confidentially. Truly, I'm just trying to figure out what the heck Blackboard might be doing, since I'm not aware of any gradebook calculation problems in 7.1 like we had in some earlier versions. It's pretty easy to manually run the numbers and compare if you're doing item weighting like Ms. Paliatka, but category weighting seems to end up more convoluted (at least to me!).

Thanks for clarifying the exam section weighting a bit more. It sounds like you actually do the section weighting in Excel before you enter the grades into Blackboard, that right?

Mike
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Okay, I ran some sample numbers to illustrate the problem. I entered grades in three already-set-up assignments, worth 10, 20 and 10 points respectively. The student scored 9, 17, and 8 in that order. Blackboard (set up to weight Assignments at 60 and Exams at 40) and Excel (set up to average these three scores and display them as a percentage) both calculate them to collectively average 85. I then added an exam grade of 74 out of 100 possible points. Blackboard then calculated the Running Total as 77.14 and the Running Weighted Total as 76.3 (both are set to exempt ungraded assignments). Excel reports the overall course average as 80.6. The formula I set up to obtain that average is =SUM((C3*0.6)+(D3*0.4)), where cell C3 contains the assignment average (85) and D3 contains the exam average (74).

Please let me know what your results are, and whether you see any errors in how I have set up either my Excel or Blackboard gradebooks.

Thanks
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Hi George,

I looks like your assignments are worth different point values. Am I correct there? The formula that Blackboard uses to accurately calculate a weighted total requires that all point values within a certain category are worth the same amount.

For example, if you have 3 assignments, they all need to be set up with same number total points of say, 10. (The assignment worth 20 pts. is likely skewing the formula and results.)
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You are correct that different assignments are worth different point values. I'm surprised that Blackboard would require all the entries in a category to have the same point values. If that is indeed the case, there should be a statement to that effect somewhere, or even better, Blackboard should send up an error message when I create a new entry within an existing category with a different point value.

At any rate, in several of my classes, I've had the same assignments with the same differing point values for a number of years, and *most* of the time (i.e., except for the current version and the previous one with the acknowledged calculation glitch), I've been able to get Blackboard and my Excel gradesheets to agree. If the requirement that all entries in a given category have the same point value is a change from previous versions, then Blackboard is going to be a lot less useful to me. If I have to calculate all entry scores on a 100-point basis in Excel before I enter them in the Blackboard gradebook, it will be easier for me to post a copy of my Excel grades online instead.
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Hi George,

You are correct, and many instructors would prefer to operate the weighted area as you are. The good news is that Blackboard is looking into enhancing the gradebook in a future release.

Here is the link to the manual with the "notice" about weighted categories: http://library.blackboard.com/docs/r7/71/en5FUS/instructor/bbas5Fr75F15Finstructor/weight_grades.htm
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Thanks for the info. I read the information at the link you provided, but saw nothing that indicated that every item within a category had to have the same point value. In fact, it used the example of two exams, one worth 50 points and the other worth 15 points. Each of the two exams would be weighted the same, i.e., if these two exams were the only ones in the Exam category, then each would be worth the same percentage of the grade, regardless of how many points each was worth. This is exactly how I wish Blackboard to treat each of my entries in a particular category. As long as I only have entries in a single category, such as Assignments, Blackboard calculates the Running Total and Running Weighted Total correctly in this manner. However, when I add an entry in a second category, such as Exams, then the calculations for both Weighted Running Total and the Running Total become incorrect.
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