Educators choose assessment grading schemes for a variety of reasons. Some may select a method that reflects the way they were assessed as students; others may just follow the lead of a mentor or instructions given by their institution.
Marking and grading are determined after all student scores for the assignment or test are assigned. Often called norm-referenced grading, curving assigns grades to students based on their performance relative to the class as a whole.
To curve or not to curve is a big question. Curving defines grades according to the distribution of student scores.
Choosing to curve grades or using a criterion-referenced grading system can affect the culture of competition and/or the students’ sense of determined fairness in a class.
Curving grades provides a way to standardize grades but yet, norm-referenced grading can ensure that the distribution of grades is comparable from time to time.
A course with a group of markers or raters, such as ‘educational studies’ that uses group of undergraduate students in the grading, may also employ a norm-referencing technique to standardize grades across sections.
In this case, standardization across a group of markers should begin with training the graders.
Curving grades should not be a substitute for instructing the group of markers how to assign grades based on a pre-defined rubric
In addition to standardizing grades, norm-referenced grading can enable members to design more challenging assignments that differentiate top performers who score significantly above the mean.
More challenging assignments can skew the grade distribution; norm-referenced grading can then minimize the impact on the majority of students whose scores will likely be lower.
A critique of curving grades is that some students, no matter how well they perform, will be assigned a lower grade than they feel they deserve. Students should have an equal chance to earn an A.
For this reason, some educators do not pre-determine the distribution of grades. The benefit of using a criterion-referenced grading scheme is that it minimizes the sense of competition among students because they are not competing for a limited number of A’s or B’s. Their absolute score, not relative performance, determines their grade.
Several ways to curve grades can be used like:
The Bell Curve where normalizes scores using a statistical technique to reshape the distribution into a bell curve. An educator then assigns a grade (e.g., C+) to the middle (median) score and determines grade thresholds based on the distance of scores from this reference point. A spreadsheet application like Excel can be used to normalize scores.
Criterion-reference grading is a pre-determined scale, assessments are based on clearly defined learning objectives and grading rubrics so students know the educators expectations for an A, B, C, etc
Clumping is when educators creates a distribution of the scores and identifies clusters of scores separated by breaks in the distribution, then uses these gaps as a threshold for assigning grades.
Quota Systems, often used in law schools, the educators pre-determines the number of students who can earn each grade. The educators apply these quotas after rank ordering student scores.
Curving can be used as a tool to adjust grades on a poorly designed test, but consistent use of curving should not be a substitute for designing assessments that accurately assess what the educators wants students to learn by the end of the course program.
Azizi Ahmad The Star Educate Star Let’s Hear It Page 6 Sunday, 21 May 2017