An instructor posed this question to me recently:

"The total weighted grade in Blackboard is different than the grade I calculate by hand. Sometimes it's higher, and sometimes it's lower, so there is no consistency.

I checked the categories and their weights, and they are correct. I tend to round up to the thousandth when I do my hand calculations. I could understand if BB was consistently lower than my calcs or consistently higher, but it's so varied.

Anyway, is there a reason why this is?"

I verified that all columns were included in their specified categories, the columns within each category were to be weighted equally, only one GC column had points awarded in excess of the possible points for that item (this 3 point overage was counted as extra credit/bonus by the instructor), no grades had been entered as a Letter (which Bb would calc at the median for the given letter grade) and worked out a few sample weighted totals from her course and arrived at the same figures as the instructor.

Please see attached example of points earned with Bb weighted total and hand calculated totals - does anyone know how Bb is figuring these weighted totals?

Any thoughts/feedback are appreciated.

Thanks,

Jessica

What do your actual calculations look like?

The "points per category" is not a relevant number to look at, since it does not really figure at all in weighted total calculations when the columns in each category are weighted equally.

If the columns in a category are weighted equally, that means that each column is first converted to a percentage (because the idea behind weighting the columns equally is that they might all be worth different points possible, and you want that to be irrelevant to the calculations). Then, the percentages are added up and divided by the number of columns, to arrive at the percent correct for that category.

Then, you take the percentages for each category and multiply them by the weight for that category.

So, for Student 1, the calculations would look like:

Category A : ((10/10) + (10/10) + (10/10) + (10/10) + (10/10) + (10/10)) / 6 = 1.00 (i.e. 100%)

Category D: (26/28) /1 = .9286

Category S: ((39/45) + (49.5/55) + (74/100) + (86.5/100) + (86.5/100) + (0/100)) / 6 = (.8667 + .9 + .74 + .865 + .865 + 0) / 6 = .7061

Category T: ((42.5/60) + (21/40)) / 2 = (.7083 + .525) / 2 = .6167

Weighted Total: (1.0 x .10) + (.9286 x .15) + (.7061 x .55) + (.6167 x .20) = .1 + .1393 + 3884 + .1233 = .751 (i.e. 75.1%)

Mike

PS: From your spreadsheet, my guess is that you are using the calculations for proportional weighting of columns in each category. If you try switching the weighted total to use proportional weighing in each category, Blackboard will probably give you the numbers you're expecting...