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Cumulative progress graphs...



Greetings. I'm sure many of you educators are in the same boat as I
am, time to figure up grades. While figuring up grades, I decided to
include the progress graphs of each of my students so that they can see
how they did over this past grading period. Our school uses Misty
City's Grade A+ Machine (Windows version). While printing out the
progress graphs, I noticed something a bit odd, the graph it was
producing didn't seem very accurate. I contacted the tech support of
Misty City and asked about the cumulative progress graph option on the
program. The tech support person responded by the following:

"I believe we corresponded about progress graphs back in October. For
the cumulative progress graph, Grade Machine averages the percentages of
each assignment. For all other reports and the grades you see in the
Grades column of the Scores window, Grade Machine first adds all the
assignments in a category or grading period, then divides that figure by
the total points possible for that category or grading period to arrive
at an average percentage. In some cases this creates a discrepancy
between the overall grade and the final plotted grade on the graph.
When you have a class with category and/or grading period weights, the
numbers can vary even more because the cumulative progress graph does
not take weights into account.

Because total points possible per assignment can vary widely, we base
calculations for the graph on a 100% scale. This formula is also less
complicated and therefore allows the graph to preview more quickly."

In other words, the cumulative graph is based upon a percentage
cumulative instead of points cumulative. All of the information about
the grades is entered as points. Other than the, cumulative graph, the
program figures the grades out just fine, but I find it odd that the
graph produced is based on percentages.
On my spreadsheet, I made up some grades to see how the two
cumulative graphs would vary. Consider the following, if student X
received the following grades:

Assignment #: 1 2 3 4
5 6 7 8
Points: 10 0 32 9
9 9 23 8
Points poss.: 30 25 50 10
10 10 25 10

Percentage: 33.3 0 64 90
90 90 92 80

Cumulative: 33.3 18.18 40 44.3
48 51.1 57.5 58.8
Cumul. %: 33.3 16.67 32.4 46.8 55.47
61.22 65.6 67.4

Hopefully you can read this, but from my calculations (Cumulative) it is
different than Misty City's calculations (Cumul. %). According to our
school's grading scale, by my calc., the student failed, but by Misty's
they passed.

My question is what is technically the correct means of calculating
the cumulative grade of a student? If I'm correct, I may write a letter
and see if they can change the way that they calculate for the
cumulative progress graph. Any help would be appreciated. I'll attach
the file I used to figure these out, it is MS Office-Excel.

Thanks,
Dwight
crvhs_dks@ncocc.ohio.gov
Ashland, OH

Attachment: grad_cumula.xls
Description: application/msexcel