Curving Exam Scores – Is it More Harm Than Good?

by Thanh-Van (Vicky) Nguyen, Pharm.D., PGY 1 Pharmacy Practice Resident, Kaiser Permanente Mid-Atlantic

When students hear the terms “curve” and “grades” used together in a sentence, they automatically assume that grades will be scaled upwards.  In fact, this is not always the case.  The act of scoring on a curve has been performed for years and is commonplace in higher education, particularly in science curricula.  However, grading on the curve has multiple meanings and, as with all other practices, there are pros and cons to grading on a curve.

Typically, curving an exam is achieved by adding points to everyone’s score in order to shift the average upward.  The score of the student(s) who performed the best on the exam is boosted to 100% and then the other exam scores are scaled up by a similar amount.  This consequently boosts all scores on the exam and often translates into higher grades for everyone.  If the procedure is rarely performed and students are not accustomed to curving, students wouldn’t anticipate receiving addition points and will likely put effort into studying.  But when curving becomes routine, potential pitfalls may occur.  Students may become less motivated to perform at their best if they know that they will automatically receive additional points.  The question then becomes whether or not curving grades accurately reflects knowledge and performance.  By curving grades, are we merely boosting students’ egos only to send them off into the world less prepared?  Does it create a false sense of security?

There are certain circumstances that may warrant curving exam scores.  For example, when creating exams, professors may misjudge the difficulty or clarity of their questions.  In these instances, it is simply unfair to punish students with point deductions due to poorly written questions.  In other situations, the subject matter may not have been taught well, resulting in poor student performance.  When the decision is made to curve scores for these reasons, its important to resolve the underlying problem.  This can be as simple as rewording future exam questions, modifying one’s teaching method, or providing additional instruction.  Unfortunately, some instructors move forward without conducting a root cause analysis or taking any corrective action.

Some proponents argue that curving can prevent grade inflation and ensures that grades are appropriately distributed among students.  In one form of curving, instructors assign grades based on a normal distribution.  The grades are distributed such that students who score near the average receive a high C or a low B.  Students above the mean would receive an A or B.  Students below the mean would receive a C or D.  Outliers are assigned an F.  This form of curving exists but it’s rarely used.  Assigning an “F” to someone who scored 82% on an exam where the class average was 93% would likely be met with outrage.  This method of curving penalizes students for not performing as well as their peers – even when they demonstrate reasonably good mastery of the material.

The procedures used to curve scores are not standardized and practices vary among professors and institutions.  Some professors review exam questions and curve based on the number of questions where a substantial portion of students got the answer incorrect.  Other professors simply bump the highest grade up to 100% and scale the rest by a similar amount.  Whether all scores should be curved across the board is another aspect to consider.  Curving can also be done selectively to help boost a few students’ scores or to reduce the number of students who fail.  This practice calls into questions fairness and smacks of favoritism.  Regardless, there is a lack of consensus regarding the best method of curving.  There comes a point when curving no longer accurately represents student learning but rather a manipulation of numbers.

There is a time and place when curving grades may be appropriate but the practice should not be commonplace.  When curving scores becomes a routine practice, it’s time to re-evaluate the teaching and evaluation methods.

References

1.  Kulick G, Wright R. The Impact of Grading on a Curve: A Simulation Analysis. International Journal for the Scholarship of Teaching and Learning. 2008;2(2):1-17. 

2.  Bradley B. To Curve or Not to Curve: Norm-referenced Grading vs. Criterion-referenced Grading. Focus on Faculty. 2005:3-4.