<p>but you see, in the end that's what letter grades come from. they come from percentages. think about it. most professors take the percentages they assign on tests, homework, quizzes, etc. and convert them to letter grades. how else can they accurately average out all those letter grades. even converting letter grades to the 4.0 scale doesn't give you an accurate picture of the grade the student gets when you have to convert it back to a letter grade.</p>
<p>you can try to do it from letter grades, but then that gets inaccurate. as an example, take a class that grades the following: 40% final, 40% midterm, 20% paper. This one student got an 85 on final, 95 on midterm, 70 on quiz in this class.</p>
<p>take the letter grade system that's commonly used with -'s = x.33 and +'s = .67
A = 93+ (4.0)
A- = 90-92
B+ = 87-89
B = 84-86 (2.0)
B- = 80-83
C+ = 77-79
C = 74-76 (2.0)
C- = 70-73
D+ = 67-69
D = 64-66 (1.0)
D- = 60-63
F = below 60</p>
<p>convert the percentages to give a letter grade for the final grade.</p>
<p>so we know the student got a B on final, A on midterm, C- on quiz (or a 3.0, 4.0, and .67, respectively). do the conversions to get the final grade and you get (3.0<em>.40) + (4.0</em>.40) + (1.67*.20) = 1.2 + 1.6 + .334 = 3.134. of course this 3.134 doesn't exist on a letter grade system, the professor has to round off to a B (3.0), but some professors might choose to give you a B+ since you did slightly more than a B.</p>
<p>OR</p>
<p>convert those grades from percentages and leave them as is.</p>
<p>(85<em>.40) + (95</em>.40) + (70*.20) = 34 + 38 + 14 = 86. the professor has no other choice but to give you a B. there's no question about it, unless the professor doesn't stick to the grading rubric he has set (and not all do).</p>
<p>also all those problems you mentioned, could be used against any other grading system. As for your examples, professors curve, that's how they assign grades even in a percentage system when average student gets very low grades. I know this because I had a high school math teacher who gave near impossible problems to us and deducted points for every little mistake we made. The class average on tests low 20s and the range was around 15-30. On that scale anyone who had the 30 or higher got the 100, a 23 got 75, and so on. it even happens in college. one of my IT professors had a test in which the class range was from 22 to 36. Took the same approach and showed us the conversions in class from percentage to letter grades. and even for professors who give extra credit on tests and homework, in the end you still max out, whether it's a percentage system or letter grade system. For example say you got 105 in a class, you're not going to get an A+ in a school that doesn't give out an A+. It'll still show up as an A. And likewise in percentage grading systems, it'll show up as a 100. Just means you did more work to ensure you got the max grade.</p>
<p>percentage grades aren't arbitrary, they are accurate. even for essays. in fact last semester i had 2 professors who combined letter grades for papers. I had on one paper a grade of B+/B which was an 86.5. Happened on tests too. Got a A-/B+ which was a 89.5.</p>
<p>i think the reason most students like it is because it can hide the fact that they may not have done the same work as the other student that got the A, but for anyone who looks at the transcript it's still an A even if you really got the 93 and the other students who got an A got 99.</p>
<p>in my head i always convert letter grades to percentages. and it shows me so far that i've been right around my high school and middle school average which is A-/B+. it definitely looks nicer on a 4.0 system, i'll tell you that much.</p>