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This post will give you a detailed analysis and understanding of how CET scores are equated and percentile scores are calculated. We will be using CET 2015 raw scores to improve this understanding and also take a look at what went wrong last year and how it impacted CET 2015 aspirants.

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MAH-MBA/MMS-CET 2015 was conducted on 14th and 15th March 2015 in 2 sessions each. Number of candidates appeared for the examination date wise and session wise:

Now, we know that CET 2015 was probably the worst year for CET aspirants. All the sessions had wrong questions, errors. And because of this the scores for every slot were converted to scores out of 200. For example, slot 1 had 19 incorrect questions hence the scores that students got were from 181. Someone who got 165 from 181 in the first slot, had 182.32 score out of 200 (Simple math: 165*200/181)

All the scores were converted to base 200 in this manner. Sounds fair so far. What was the issue then? The biggest problem was the difficulty levels of the individual slots. We looked at the raw and converted scores of all the candidates in each of the slots. Look at the shape of the Day 1 Slot 1 and compare it with the remaining three slots.

Day 1 Slot 1:

Average score 100.984, Median score 101.105, Standard deviation 46.9

Day 1 Slot 2:

Average score 90.967, Median score 91.209, Standard deviation 45.3

Day 2 Slot 1

Average score 91.449, Median score 91.534, Standard deviation 46.1

Day 2 Slot 2

Average score 84.61, Median score 84.65, Standard deviation 43.1

Because of this varying difficulty level, DTE used the equated scores. The explanation which was given behind this decision was:

As the examination is conducted in multiple sessions, the question papers were different for each session, the marks scoring pattern depends upon the difficulty level and it varies from session to session. Due to this variation, DTE has normalised the score using Equipercentile Method to take care of the difference in difficulty level, so that no candidate feels he/she is at a loss because he/she attempted a session which had tougher set of questions.

Percentile scores in the respective batch were calculated batch wise i.e., Batch I, Batch II, Batch III, and Batch IV using the following formula:

Batch II percentile scale was considered as Reference, as the number of students appeared in the the second slot were more. Equated score for the percentiles that are not present in the percentile of Batch II were calculated by interpolation. Linear Interpolation is worked out in the following way:

Where
Y = Equated Score rounded up to 2 decimal places
Y1 = Marks corresponding to immediate lower percentile form Batch II
Y2 = Marks corresponding to immediate upper percentile form Batch II
X1 = Immediate lower percentile form Batch II
X2 = Immediate upper percentile form Batch II
X = Percentile of the Candidate of the respective Batch

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