Are exams suppose to evaluate how well you have learned ? Then, by this standard, almost all exams are rigged. Over time we have somehow come to deceive ourselves. There is a simple test to tell us if we are truly testing childrens abilities. I need to explain.
For any test you give find the distribution of the marks children have got. You can do this by counting the number of children who got marks between 0-20, 20-40, 40-60, 60-80 and 80-100. Now plot the number students against marks between 0-100. If the test is fare and balanced you should get a curve that looks like the following.
If you were to plot the distribution of height of students in your class, you will also get the same Bell-shaped curve. How is it that such widely different things give you same curve ? Well, many things in life follow this curve because there is a range of competencies (or heights). But they are not totally random, they stay close to average competency or the average height.
In this Bell-curve you will have majority of students getting close to 50%, some are getting less and some are getting more than 60%. The average marks should be close to 50%. In such exam it should be easy to get above 30% and difficult to get above 70%. It would test everyone in class - those who are slow to learn and those who are fast to learn.
When the distribution of any measurement doesn't follow the Bell-curve, it may have many reasons. But the two most likely reasons are - either our class (or sample) was not balanced with a range of students, or our test was not balanced with a range of questions.
I bet that for most of the exams the Bell-curve is not balanced and centred at 50%. Most children get above 60%, many are close to 80% and a only a few get bellow 30%. The Bell-curve is considerably distorted and shifted to far right. The shifted and distorted curve is telling us that we are making it far easy for under-performers and we are dumbing down high-achievers. We are moving most of the class into average performance zone. This means that we are not differentiating under-performers and high-achievers well.
This is not surprising given that none of us, parents, teachers or students, want to take any risk. We want students to do well and move onto the next grade. Marks are usually like a barrier to cross. Once you are over it, you go to the next grade. Our exams reflect these desires. Exams act like a filter to promote students and not to evaluate competencies. We aren't treating marks as indicators of performance, but only as licence to get to the next grade.
However, this is perpetuating a larger tragedy. When the distribution is not Bell-shaped and centred at 50%, we failing to identify under-achievers and their deficiencies. We are also failing to recognize the true high potential of high-performers.
So next time you look at marks, as a teacher or a parent, ask for the distribution plot, Does it look like a balanced Bell-curve ? and ponder !
For any test you give find the distribution of the marks children have got. You can do this by counting the number of children who got marks between 0-20, 20-40, 40-60, 60-80 and 80-100. Now plot the number students against marks between 0-100. If the test is fare and balanced you should get a curve that looks like the following.
In this Bell-curve you will have majority of students getting close to 50%, some are getting less and some are getting more than 60%. The average marks should be close to 50%. In such exam it should be easy to get above 30% and difficult to get above 70%. It would test everyone in class - those who are slow to learn and those who are fast to learn.
When the distribution of any measurement doesn't follow the Bell-curve, it may have many reasons. But the two most likely reasons are - either our class (or sample) was not balanced with a range of students, or our test was not balanced with a range of questions.
I bet that for most of the exams the Bell-curve is not balanced and centred at 50%. Most children get above 60%, many are close to 80% and a only a few get bellow 30%. The Bell-curve is considerably distorted and shifted to far right. The shifted and distorted curve is telling us that we are making it far easy for under-performers and we are dumbing down high-achievers. We are moving most of the class into average performance zone. This means that we are not differentiating under-performers and high-achievers well.
This is not surprising given that none of us, parents, teachers or students, want to take any risk. We want students to do well and move onto the next grade. Marks are usually like a barrier to cross. Once you are over it, you go to the next grade. Our exams reflect these desires. Exams act like a filter to promote students and not to evaluate competencies. We aren't treating marks as indicators of performance, but only as licence to get to the next grade.
However, this is perpetuating a larger tragedy. When the distribution is not Bell-shaped and centred at 50%, we failing to identify under-achievers and their deficiencies. We are also failing to recognize the true high potential of high-performers.
So next time you look at marks, as a teacher or a parent, ask for the distribution plot, Does it look like a balanced Bell-curve ? and ponder !
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