They take into account the variations in examinations conducted by different Boards, he said.
Based on this year's examination data, the cut-off percentile score for top 20 percentile varies from one Board to another.
Since different Boards evaluate differently, percentiles have been used to ensure a fair comparison of students belonging to different Boards.
In the new scheme of the Joint Entrance Examination (JEE) (Advanced), only the top 1.5 lakh candidates (including all categories) based on their performance in the JEE (Main) qualify to appear in the JEE (Advanced) examination.
The admissions to the Indian Institutes of Technology (IITs) are based only on their category-wise All India Rank in JEE (Advanced), subject to the condition that such candidates are in the top 20 percentile of successful candidates in class XII examinations conducted by their respective Boards in applicable categories.
The admission to the National Institutes of Technology (NITs) are based on combined merit list created by giving 40% weightage for performance in class XII Board marks normalized on percentile basis with the remainder 60% weightage for performance in the JEE (Main).
This system has been applied uniformly to all the candidates, and, therefore, the chances of students getting affected does not arise.