Thursday, January 20, 2011

Geometry Finals and Grade Scales

The Geometry Final Exams are scored and in Skyward.  Grades are not yet finalized as I have a small stack (pronounced "Mountain") of makeup quizzes, absent work and other things to enter.  Overall the grades were good and I am proud of all my geometry students and the success they showed me on their exams.

I did want to take a moment and explain grade scales because I can with the data I have here:

The traditional scale, and the one used on this final is the standard 10% split for all grades.  The exam was out of 75 points so the scale goes like this:
A:  75-68, B:  67-60, C:  59-52, D:  51-44, E:  44 and down

Now for one of the two classes, I won't say which, the mean score was a 64, median was 67, and there was a Standard Deviation of 15 points.  So if we had used a Curve to figure the grades we'd have a different scale:
A: 75  B: 74  C:  73-59  D:  58-43  E:  43 and down

That means that to get an A you had to have landed right smack dab on a perfect paper.  Why?  Well remember that with a true Curve, the objective is to have the majority of your scores be considered "average" or a C.  With this grade break down, because everyone did so well, it pushes that curve upwards and makes a B and an A harder to get.  Also, remember that with a Curve you should have roughly the same number of A's (3 students out of 30) as you do E's (3 students out of 30). 

Because grade curves are highly competative, I generally don't use them.  They just put too much presure on students to do better than their peers rather than to do the best they can do.

No comments:

Post a Comment