Physics 100 - Spring 2009 - University of Rochester
Physics of the Natural World
Mean best numerical average was 84
The Best Numerical Average (BNA) is your final average in the course where I have calculated it three different ways (see below) and used the best number for each student. This is the distribution I used to determine letter grades in the course. A was >= 89, A- was from 86-88, B+ was from 81-85, B was from 72-80, B- was below that. For various reasons, I didn't feel it necessary to give anything below that in this course this year.
Several of you took a huge hit in your BNA because of very low recitation attendance and problem set scores, both of which factor in directly into the BNA. I looked at this carefully because it was not my intent that you drop a couple of letter grades due to having not done the problem sets/recitations, though some penalty is appropriate. It turns out that since the spread in letter grades is generous and wide, those of you taking a big hit in BNA due to this ended up only dropping one notch or less in the grade scale (say B to B-).
In calculating the BNA, I used your normalized exam grades (as mentioned in the syllabus). That means I normalized the mean of each exam to 75 by scaling each exam score by the ratio 75/(mean for exam). This is the way I correct for the exams varying in difficulty. It's a necessary correction to put in when I have a scheme where you are allowed to drop a grade, such as the one we are using. So, before calculating the averages below, your exam 1 grade was multiplied by 75/78, since the mean of exam 1 was 78. For exam 2 the normalization factor was 75/81. For the Final exam the mean was 75, so no normalization was necessary. You can verify the calculations from the information I provide for you on BlackBoard. The BNA was calculated three ways for each person (as below) and I took the best number for each student as that individual's BNA.
Scheme
Exam 1
Exam 2
Final exam
Present.
Prob. sets
Recitation
1
---
22%
30%
20%
14%
14%
2
22%
---
30%
20%
14%
14%
3
16%
16%
20%
20%
14%
14%