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Points vs. Percentages: Calculating your grade

You may have noticed that each teacher has his or her own system for evaluating classes.  With all of the variation, how are you supposed to figure your final grade?  There are a few basic systems that most instructors use.  When in doubt, ASK!

The two main systems are very similar.  One system assigns points to each assignment or exam, and then assigns the grade distribution based on the number of points you have accrued.  The other system records the percent correct that you receive on each assignment, exam, etc.  At the end of the semester, your total percentage in the course is used to assign your letter grade.


Points

Some instructors will tally the total number of points earned in a semester, and then will assign letter grades accordingly. 

For example:      

Hour Exams     300    A         660 points
Final Exam       200   AB       640
Laboratory       200   B          575
Other               100 BC       555
800   C         500
  CD      480
  D         400

In this example, the instructor has listed his assessment items (hour exams, final exam, laboratory work, and "other") and how many points are available in each. 

Maybe, you received the following points:

Hour exam 1 80
Hour exam 2 78
Hour exam 3 96
Final Exam 124
Lab work 175
Other 80

Total 633

You totaled 633 points in the semester.  According to the grading scale, you would receive a "B" in the course.  Congratulations! 

Advantages

There is very little math involved, and it becomes extremely easy to calculate your grade at the end of the semester.  All you need to do is count and add! Many people prefer this method because they don’t need to worry about calculating percents for each assignment or exam. 

Disadvantages

As you can see, your total number of points determines your grade.  If you are one point shy of the next grade level, it can be much more frustrating!  It can also be more difficult to see where the importance is put in a course—which is worth more:  an exam, quiz, or individual homework assignment?


Percents

This is the "classic" method of grading.  You still get a specific number of points on each assignment; instead of merely looking at the sum of all of your points, you look at the percent of points you earned on all of your assignments.

For example:

Grading Curve
Homework 25% A 90-100 C 70-74
Quizzes 25% AB 85-89 CD 65-69
Midterm Exam 25% B 80-84 D 60-64
Final Exam 25% BC 75-79 F Below 60

In this method, you take the average of all of your points in each grading category.  In this case, there are four: homework, quizzes, midterm, and final.  To begin, find the average of all of your homework assignments.  From the chart above, you can see that this is worth 25% of your grade.  The average of all of your quizzes is 25% of your grade.  Your midterm and final exams are each worth 25% of your grade.  When you compute your final grade, you can "translate" your percentage into a letter grade using the curve above.

Perhaps you earned the following points:

Homework (out of 10 points) Quizzes (out of 15 points) Midterm Exam:  100 points
Homework 1 8 Quiz 1 15   88
Homework 2 7 Quiz 2 13    
Homework 3 6 Quiz 3 12 Final Exam:  200 points
Homework 4 9 Quiz 4 15   184
Homework 5 10 Quiz 5 10    
Homework 6 10 Quiz 6 14    
Homework 7 8 Quiz 7 15    
Homework 8 9 Quiz 8 13    
Homework 9 8 Quiz 9 15    
Homework 10 6 Quiz 10 14    
Total: 81   136    
Average: 81/(10pts*10 homeworks) =0.81 or 81% 136/(15 pts *10 quizzes) =136/150=0.907 or ~91%  

After determining where you stand on your current assignments, you can figure out an approximate final grade.  

Calculate the total points you received on all of your homework assignments.  Next, calculate the total possible points earned on your homework assignments.  You need both of these numbers to calculate the percent correct you have earned.

You received 81 total points out of your homework assignments.  You received an 81% for the homework portion of your grade (so, by the curve above, about a B average).

You can do the same for your quiz grade.  Your quiz grade is 90.7% (an A average).

Your midterm exam grade is 88%.  You received an 88%, or an AB on the midterm.

Your final exam grade is 92%.  You received an A on the final.

Now, you are ready to determine your final grade, as follows. Take the amounts you earned in each individual section; multiply them by the percent each section is worth.  See below example:

Grading Your grade * % section is worth = =20.25
Homework 81*.25 =22.675
Quizzes 90.7*.25 =22
Midterm 88*.25 =23
Final 92*.25  

Total   87.925

Your total is 87.925.  By looking at the chart above, you would get an AB in the course.

Advantages

With percents, you can see how you are doing throughout the semester.  It is easier to get an idea of how you are doing when all assignments are in.   

Disadvantages

It becomes much more difficult to argue "one more point" to raise your grade.  Since percents are based on your averages for your class, they are more indicative of how you are doing as a whole.  One assignment is less apt to make or break your grade.  There is also more work involved in computation (as you can see!).


Curves

There are many, many different types of grading curves. 

Bell Curve

The standard curve is commonly called a "bell" curve.  In this case, there is a specific number of each letter grade allowed.  For example, in a class of 20, the top grade in the class would get an A, and the lowest grade would be an F.  The middle 8 or so grades would be a C, and the rest become AB, B, BC, CD, or D.  This curve will rank you in terms of your classmates.  It is a system that can cause a large amount of animosity, and does not lend itself well to collaboration between students! 

Pre-set Curve

Some people call their specific grade distribution a "curve."  For example, one instructor at Edgewood uses the following:

90 - 100% A
88 - 89% AB
80 - 87% B
78 - 79% BC
70 - 77% C
68 - 69% CD
60 - 67% D
Below 60% F

The "curve" is already set, at the beginning of class.  If you receive anywhere from 90-100% on your work, you would receive an A.  In this type of curve, you are competing only against yourself. 

Random Curve

Occasionally, you can find the following statements in a syllabus:

"Keep in mind that this scale may change based upon overall class performance, but it will only be adjusted downward"

"This curve may be adjusted but only at the end of the semester after the final exam is graded and the numerical averages are completed."

This type of curve is put into place for your benefit!  It means that the instructor had a specific "pre-set" curve in place when the semester started.  After looking at all grades at the end of the semester, he or she may decide to adjust the scale to allow more students to receive As, Bs, Cs, etc.  This type of curve will not harm your grade in any way; instead, it may boost you from an AB to an A!