CUET-UG: What are ‘normalised’ NTA scores and how varsities will rank students?

“The rank lists will be prepared by universities using normalised NTA (National Testing Agency) scores and not on the basis of percentile. The scores have been normalised to provide a level playing field for students since they wrote test in the same subject on different days,” Kumar said.

“Normalisation of CUET scores has been done separately for each subject for which the exam was held in multiple shifts,” he added.

However, the decision has left many confused as they don’t understand the concept of “normalised” scores and how they can be used to set the rank list. 

Why CUET is using “normalised” scores instead of percentile? 

In single-session entrance tests, one common statistically established method is used to transform the raw marks into a common uniform scale using the percentile method so that the performance of students can be compared to each other.

CUET-UG has been conducted on 27 different subjects with the freedom to choose a combination of these subjects. Moreover, the tests were conducted on different days and in multiple sessions for the same subject. This obviously gives rise to multiple percentiles for each group of students. 

In addition to that, in subjects such as Sports or Fine Arts, some weightage (e.g. 25%) is given to the skill component by some universities. But, the addition of raw marks in the skill component and the remaining weightage (75%) of percentile cannot be done to prepare the rank list because it would be similar to adding oranges to apples.

Hence, to find a solution to this problem, UGC resorted to “normalised” scores to prepare the rankings. 

What are ‘normalised’ NTA scores?

UGC adopted the normalisation formula using the equipercentile method. For this, percentile for each candidate is calculated by comparing their raw marks with other candidates in the same session. These percentiles are then equated, and converted into normalised marks. For sessions with smaller number of candidates, these are clubbed with bigger sessions.

For example, in a particular university, if the raw marks of the skill component has certain weightage (e.g. 25%), they can be added to the remaining weightage (e.g. 75%) of the normalized marks to prepare the rank list. 

It is important to note here is that for each subject for which examination is held in multiple shifts, raw marks are converted into normalised marks on a common scale, UGC said in its circular. 

How the candidates will be ranked? 

Step 1: Using raw marks of the students in different shifts, the percentiles of students in each shift will be calculated. 

Let us say in a given shift, 100 students have appeared for the test. We sort their marks in decreasing order. Let us assume that one student among these 100 students has scored 87 % marks. Now let us assume that 80 out 100 students have secured less than or equal to 87% marks. The percentile of this student with 87% marks would be 80/100=0⋅8, UGC said

Step 2: These percentiles will be arranged in a descending order by noting the raw marks of the students in each shift.

Let us now assume that there are six students. Three of them have taken the test in shift-1 and the remaining in shift-2 but all in the same subject. Using the raw marks of these students, first the percentiles of these six students in a given subject are calculated and are sorted in a decreasing order. Their Raw Marks in the test in each shift are also noted corresponding to their percentiles

Step 3: Using linear interpolation, the marks will be calculated 

Since some students have attended shift-1 and not shift-2, their raw marks in the shift-2 will not be present. Similarly the students who wrote the exam in shift-2, will have no marks in shift-1. These missing marks of each candidate in each shift are then calculated using a method called interpolation.

Interpolation is a mathematical way of estimating missing marks of the students who are absent in one shift because they have already taken the test in the other shift.

Step 4: Normalized marks will be calculated on a common scale

Using the above method, each percentile value of the candidates sorted in a descending order will have marks for both shifts, raw marks and interpolated marks.

Raw marks are available in the shift where the student has written test and interpolated marks are estimated in the other shift because the student could not have written test for a second time in the same subject. For each student, we then calculate the average of the actual raw marks in one shift and the marks obtained using interpolation in the other shift. This will give the normalized marks for the corresponding percentile of each candidate.