Grading On Bell Curve: Bell Curve Grading System
Bell Curve Grading, also known as grading on a curve, is a grading method teachers use to avoid inflations in grades. In this grading technique, students are assigned grades relative to the performance of their classmates. It is not individually measured but instead on the basis of the whole class’ grades and performances. It is in concord with the percentile technique, where a student’s performance evaluation occurred on behalf of all other participants. Grading on a curve is not coherent with other grading techniques like relative or absolute grading systems. This grading system has its pros and cons, which we will discuss further. Checkout related guide on GPA calculator
Example of Grading on Curve
Let’s assume that a professor has a class of 10 students. Now, Grading in the curve does not allow all students to get the same grades or all students to get high grades, which lies within some range like all 85% will grant A+, Nope. This grading system works on the performance of the whole class. The teacher first does some mathematics and then will deduce a strategy and a grading scale. This grading scale will always vary as per the performance of students. How a Teacher calculates the grading on a curve is discussed further step down. Checkout related guide on CGPA to Percentage
How Does Grading On a Bell Curve Work
STEP 1 :
| Step | Calculation/Description | Result | Explanation |
| Collect scores | Raw Scores from Professor’s Class | 95, 85, 82, 78, 74, 70, 68, 65, 60, 55 | For example, a professor has 10 students who got the following marks in his subjects. |
| Calculated Mean | Mean= ∑Scores / Number of Students | 732/10 =73.2 | He added all the marks and then divided them by 10. |
| Calculate Standard Deviation (SD) | Use calculator for this or online available tools | 12 | We used an online tool to calculate standard deviation as per our student’s data. |
| Determine Grades Cutoffs Based on Mean and SD | |||
| A | Mean+1×SD | 73.2+12=85.2 | Now, teachers in different colleges will use other criteria like adding 1 in the Mean, adding 0.5, and adding 1.5 as per the college criteria or the difficulty of the course and students’ performance. |
| B | Mean to { Mean+1×SD } | 73.2 to 85.2 | The formula explains the range; within this range, the students will be awarded B. |
| C | Mean−1×SD to {Mean} | 61.2 to 73.2 | It is the same as explained in the above step. |
| D | Mean−2×SD to { Mean−1×SD } | 49.2 to 61.2 | The professor specifies both the start and end of the range as per the college criteria. |
| F | Below to {Mean−2×SD} | Below 49.2 | Below this number will be awarded by F. |
STEP 2 : Applying the Cutoffs to Scores
Cutoff: Cutoff is a common term in the grading system or assignment of grades which means the boundary of the grade assignment. Students who secure more than 85.2 marks will receive an A in the subject grade. Here, 85.2 is cut off. Checkout related guide on Percentage to CGPA.
| Raw Scores | Calculations | Grade |
| 95 | >85.2 | A |
| 85 | 73.2≤Score<85.2 | B |
| 82 | 73.2≤Score<85.2 | B |
| 78 | 73.2≤Score<85.2 | B |
| 74 | 73.2≤Score<85.2 | B |
| 70 | 61.2≤Score<73.2 | C |
| 68 | 61.2≤Score<73.2 | C |
| 65 | 61.2≤Score<73.2 | C |
| 60 | 49.2≤Score<61.2 | D |
| 55 | 49.2≤Score<61.2 | D |
STEP 3 : Grade Distribution as Per the Cutoffs Applied in Earlier Steps
| Marks of Students | Score Range | Assigned Grades |
| 95 | >85.2 | A |
| 85, 82, 78, 74 | 73.2 to 85.2 | B |
| 70, 68, 65 | 61.2 to 73.2 | C |
| 60, 55 | 49.2 to 61.2 | D |
| None | <49.2 | F |
Summary of the Process
| Student | Raw Score(score students obtained ) | Deviation from Mean (obtained marks – mean) | Z-Score (deviation/standard deviation which is 12) | Assigned Grades |
| 1 | 95 | 95 – 73.2 = 21.8 | 21.8/12=1.82 | A |
| 2 | 85 | 85 – 73.2 = 11.8 | 11.8/12=0.98 | B |
| 3 | 82 | 82 – 73.2 = 8.8 | 8.8/12=0.73 | B |
| 4 | 78 | 78 – 73.2 = 4.8 | 4.8/12=0.40 | B |
| 5 | 74 | 74 – 73.2 = 0.8 | 0.8/12=0.07 | B |
| 6 | 70 | 70 – 73.2 = -3.2 | -3.2/12= – 0.27 | C |
| 7 | 68 | 68 – 73.2 = -5.2 | -5.2/12= – 0.43 | C |
| 8 | 65 | 65 – 73.2 = -8.2 | -8.2/12= – 0.68 | C |
| 9 | 60 | 60 – 73.2 = -13.2 | -13.2/12= – 1.10 | D |
| 10 | 55 | 55 – 73.2 = -18.2 | -18.2/12= – 1.52 | D |
Bell Curved Grading System Calculator – Grading Bell Curve Calculator
It might be challenging to provide a generic tool for the Curve grading system due to the variability in grading policies, subjectivity in judgment, and context-specific considerations. It is always better to conduct a manual calculation for the grading bell curve. I used the example case study in the above step. Following the hierarchy, one can easily understand and perform this grading system to calculate grades as per their college policy and with a personal subjective approach. Checkout related guide On calculate CGPA.
Bell Curve Grading Formula
Following is the Curve Grading Formula given
- First, take the mean of all the course student’s marks.
- Take the standard deviation of the marks.
- Subtract the individual score from the mean of the scores.
- Divide each score by the standard deviation.
- Now the professor will use a standardized approach by deciding that the top 10% or 5% of students will get A grades and the next top 20% will get B grades.
- Apply cutoffs, and there, a grading scale is ready. Checkout related guide on GPA Scales
Difference between Bell Curve and Standard grading system
| Standard Grading System | Bell Curve Grading System |
| Standard grading system also depends upon the professor or college policy, but once it is stated, in most cases, it is used as standard policy. The student immediately calculates his grades as per the standard calculations like one who gets More than 85% of marks will receive A More than 75% of marks will receive B+More than 70% of marks will receive a B, etc. | However, Grading on a curve shows high uncertainty in grading policy every time the result concludes, even for the same teacher for different subjects or the same subject in other semesters. Professors use grading criteria as on the difficulty of the subject, exam, class performance, etc. Students are awarded with grades as percentile metric. |
Advantages of the Bell Curve Grading System
Fair Grading system: It helps to reduce the effect of very easy or very difficult exams by conducting assignments of the grades on the basis of whole class performance.
Competition: It produces a competitive environment; students make an effort to overbeat their fellows.
Relative performance: Recognizes top performers even if the entire class scores lower than expected.
Disadvantage of Bell Curve Grading
Grade Scarcity: A fixed number of students must receive lower grades regardless of their efforts, performance, or understanding of the course.
Stress and Competition: This may increase stress and unhealthy competition among students.
Frequently Asked Questions
Is the bell curve grading system fair?
It is a subjective approach that the fairness of the process can only be judged by how the grading policy is designed and proposed for the well-being of students and the college.