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Part IA

Marking and Classing

The following marking scheme has been approved by the Committee of Management for the Natural Sciences Tripos.


Examiners are nominated by the various Faculties and Departments who contribute to teaching on the Tripos and are formally appointed by the General Board. In each subject, there is a Senior Examiner and other appointed Examiners and Assessors who are responsible for setting the papers and marking the scripts. There is also a Chairman of Examiners who, along with the Senior Examiners, assigns classes to candidates and produces the class list and final markbooks.

Marks from individual subjects

In each subject, the Examiners produce a mark for each candidate.

For many subjects, the final mark will consist of a component from written papers and a component from continually assessed work or written practical examination. The marks for these two components are also submitted separately; they should add up to the total mark and it should be made clear how marks out of 100 are allocated to each component.

Marks for each subject are norm-referenced for candidates sitting that subject. The marks are scaled such that:

  • 25% of candidates achieve a mark of 70.0-100.0
  • 65% of candidates achieve a mark of 50.0-69.9
  • 10% of candidates achieve a mark of 0-49.9

A fail is thought of as 40.0 marks and below; note, however, that in Part IA of the NST a failure in a single subject is of no particular consequence other than the low mark.

Experience indicates that large subjects (those with, say, more than 150 candidates) should have no difficulty reaching these targets to within a few percent. Smaller subjects are not expected to hit these targets so closely.

Examiners should use their discretion over the 10% target for the bottom section of the ranking category. Experience is that the numbers who can reasonably be placed in this band do tend to vary very much from year to year, even in large subjects.

If a Senior Examiner feels that there are compelling reasons to deviate from these targets he or she must discuss this with the Chairman of Examiners well in advance of the final meeting.

Submitting marks

The final (aggregate) mark will be expressed as an integer in the final markbook, but as there may be intermediate stages of manipulation it is required that marks from individual subjects be submitted rounded to one decimal place.

Classing procedure

Each subject generates its own absolute scores for its (usually 2) papers.  Marks are rounded to the nearest integer (for example, 45.4 becomes 45 and 45.5 becomes 46) and final marks are then used by the Senior Examiners to determine an order-of-merit for the field of candidates, who are then assigned classes for the Tripos such that:

  • 25% of candidates for the Tripos achieve a 1st class
  • 67.5% of candidates for the Tripos achieve a 2nd class
  • 7.5% of candidates for the Tripos achieve a 3rd class or fail.

The order-of-merit compiled by the Examiners is used as a tool to aid them in determining the overall performance of candidates. It is not meant as a firm indicator of any individual candidate's relative standing in the field.

Small deviations from these percentages may be justified (especially in the 3rd class and fail categories) depending on the field of candidates.

Candidates who achieve less than 39% of the full mark will not necessarily be awarded honours, although this will be a decision of the Examiners.

The final boundary marks used and the number of candidates in each class are included in the final markbook which is sent to Colleges.