Home > General Musings, Grading Schemes > The Merits and Demerits of Grading on a Bell Curve

The Merits and Demerits of Grading on a Bell Curve

This entry will touch upon the good, the bad, and the ugly aspects of grading on the infamous ‘Bell Curve‘.  For those of you unfamiliar with either this grading practice, or normal distributions in general, let me briefly elaborate:

Now, for the sake of brevity, I will try to spare you from all of the mathematical gobbledygook and statistical mumbo-jumbo that traditionally comes with these sorts of explanations.

1.  What exactly is a bell curve?

A bell curve, or more specifically, a Gaussian Distribution, is a symmetric curve that is pronounced in the middle, and tapered off at the edges (it really does look like a bell).  As such, the middle portion under the curve contains more area than either of the ends.

 

This is what a typical bell curve looks like.

 

2.  What does “grading on a curve” mean?

When courses are said to be “marked on the curve,” this usually means that a predetermined percentage of students will obtain each grade.  For example, a certain amount of students will receive an A+ (top 4%), a certain amount will receive an A (next 7%), and so on and so forth.  Ultimately, the distribution of grades will fit ‘nicely’ on a bell shaped curve; with the majority of students obtaining marks near the middle portion of the curve (‘B’ range).  Unfortunately, however; this also necessitates the fact that a certain percentage of students will inevitably obtain ‘F’ grades, and fail the course entirely (bottom 6%).

——–

I am neither an ardent supporter, nor detractor, of this grading practice.  I believe that although it is beneficial in many instances, there are times and situations where it could be downright illogical to employ.  Here are some of the merits and demerits that I have conjured up after having experienced both the bright side, and the dark side of the curve:

MERITS:

- The curve is quite accurate at differentiating between student abilities when used in large classes, that is, classes with 200 students or more.  There is nothing really remarkable about this fact; all statistical methods are more accurate when the sample size is increased.  (The cream of the crop rise to the top)

- The curve fosters healthy competition.  When graded on a curve, many people like to compete amongst their friends to see who will come out with the highest mark when all is said and done.  This gives people an extra incentive to study hard and aim skyward for success.

- There is still a chance for you to achieve an A/A+ grade, even if you score poorly on the exams.  What I mean is: you’re only graded on how well you do “relative” to everybody else; thus, you are not graded based on your “absolute” performance.  For instance, if you get a 50% on your midterm and the class average was 30%, then you would likely still be in the ‘A’ range because you have scored higher than most of your peers.  Moreover, if you were one of the students who had scored 30% (with the class average at 30%), instead of finding yourself in the ‘F’ range, the curve would place you nicely within the ‘B’ range.

Demerits:

- The curve is not good to use for small classes (less than 100 students).  There is simply too much room for error.  There could be a case where 30 out of the 100 students are ‘extremely’ proficient with the course material.  Even though these students would all score in a similar range on exams, only a small percentage of them will be guaranteed to get a top grade.  This essentially makes it ‘very’ hard to get a top mark.  Furthermore, the cutoff grades may be very close to each other; it may be a mere 4% difference that separates an A+ from a B.

- The curve has the potential to foster unhealthy competition.  With the knowledge that they ‘must’ outperform their peers, some students may adopt a rather, disingenuous attitude towards their fellow classmates.  They may not be willing to provide help, or worse yet, may deliberately feed others misinformation in order to get ahead. (NB: Fortunately, I have never met this type of student; but have heard horror stories of this sort of thing happening.  For the record, most people are genuinely caring and helpful!)

- High class averages are not always favorable.  Let’s say that a certain course has a class average that is 85%.  If you were one of the students who obtained 70%, then you would be in for a rude awakening, courtesy of your ‘friend’, the bell curve.  If the average, which is 85%, would equate to a grade in the ‘B’ range, your 70% would most likely sit somewhere in the ‘C’ range, or … lower still.

——–

Next time you hear the words, “it’s graded on a curve,” don’t hastily dismiss it as a bad thing; conversely, don’t write it off as a good thing thing either.  Carefully weigh out the pros and cons; the good, the bad, and the ugly, and make sure you try your best, no matter what the situation may be.

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  1. Liu Rijing
    July 5, 2013 at 2:13 am

    I have taken a course where I did bad but obtain a B but obtain a C in a course when I did well.

  2. July 20, 2013 at 5:17 pm

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    as I’m wanting to create my own website and would like to find out where you got this from or what the theme is called. Appreciate it!

  3. September 17, 2013 at 5:34 pm

    It’s actually a nice and helpful piece of information.
    I am glad that you just shared this useful info with us.
    Please keep us up to date like this. Thanks for sharing.

  4. Patrick
    November 4, 2013 at 9:53 am

    Grading on a curve is terrible and your merits/demerits are mindboggling.
    If students can’t distinguish themselves from each other under fixed grade brackets, the answer isn’t to disconnect grades from each student’s personal performance. Let’s not mention the “differentiation” between students in the middle of the bell curve. Unhealthy competition as you define it, exists wherever a student realises other students must do worse – regardless of grading scheme. You will realise how nonsensical your first merit is, if you take your first demerit and change the numbers to ’60′ and ’200′.
    Please write a piece on “weighing up the pros and cons” of hitting my dick with a hammer.

    • Travis
      December 23, 2013 at 5:21 am

      Wow Patrick that was extreme

      Hitting your dick with a hammer. Lmbo.

      Bet that dick will have a bell-shaped curve afterwards!

  5. Hannah
    November 14, 2013 at 1:17 pm

    I thought this was extremely helpful! Thank you!

  6. Travis
    December 23, 2013 at 5:21 am

    Wow Patrick that was extreme

    Hitting your dick with a hammer. Lmbo.

    Bet that dick will have a bell-shaped curve afterwards!

  1. July 19, 2011 at 3:58 pm
  2. March 23, 2012 at 9:23 pm
  3. June 29, 2012 at 4:59 am
  4. December 21, 2012 at 12:19 am

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