This post has to do with number crunching and perhaps would be only interesting to people who are interested in that area and who perhaps want to estimate the AIR and percentile from the NEET marks.
Now that NEET marks (out of a total of 700) are available, I have had to estimate the rank of a candidate who has got, say 600, marks. I looked up this link under the section "NEET 2017 Cut-off For AIQ Seats". As per this link, 14315 students will have marks from 685-468 marks (out of 700).
Now comes the interesting part.
How do I estimate the AIR (All India Rank) of a student who has got 600 marks?
The easiest way is to assume that all 14315 student marks are spread out equally between 685 and 468. In such a case, the rank of student-600 is about 14315*(685-600)/(685-468) =5607 approx.
But then this is very likely to be grossly incorrect because it assumes that the number of students between 685 to 585 is the same as between 585 to 485. In reality, perhaps student curve may be more like a bell curve with very few students near the maximum marks and again very few students near zero or minimum marks while the majority of students will be near the middle. How do we model this?
Here I assumed that students having marks between 685 and 10 marks less than 685 (= 675) will be 20. And students having marks between 675 and 665 will be 20 times a factor that is more than 1 (say 1.3). 26 students (=1.3*20) would have got between 675 and 665. Number of students who got between 655 and 645 would be even more than 26 (I assumed it will be 26*1.3) =34. And so on. Until we get the number of students having marks between 475 and 465. If you remember, number of students having marks between 685 and 468 will be 14315.
Now that we estimated number of students in each slab of 10 marks, we can sum up and estimate the total students who got marks from 685 to 465. Now this may not equal 14315. If it is not equal then we tweak the factor which we assumed to be 1.3 until the sum total of students with marks between 685 and 465 matches 14315 more or less. And thus we get a good estimate of the number of students in each slab of marks 685-675, 675-665 and so on till 475-465.
With this, we are in a position to find out the AIR of the student who got 600 marks. That rank will be approximately the number of students who got more than 600 marks. Let's say his All India Rank came out to be 737. And let's say 200,000 students wrote the NEET exam. The percentile for the student would be (200000-737)/200000=99.63.
200000-737 being the number of students whose marks were lower than that of the student we are considering. Actually this itself is another approximation. There would have been many students who got the same 600 marks as our student. So the number of students who got lower than 600 would be less than 200000-737. But this is ok for an approximate estimate.
This is the spreadsheet which shows the calculations for NEET. Of course the estimates are heavily dependent on the assumption that 14315 students got marks between 685 and 468.
If anyone is interested in getting this estimate, you can leave a comment on this post.
There is another link which predicts NEET rank. The link predicts the ranks against marks as follows (data as on Jun 20 2017, 1PM)
Marks Estimated Rank
680 1 - 10
670 11 - 20
660 21 - 50
650 21 - 50
640 51 - 100
630 51 - 100
620 101 - 150
610 151 - 200
600 251 - 500
590 251 - 500
580 501 - 1000
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