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Part IB ESB - Examinations

  • There are two theory papers, each of three hours duration, which count towards 60% of the exam. Each paper is divided into two sections of five questions. You have to do two questions from each section. 
  • Note that past papers prior to 2015 are called Geological Sciences A and that the content of these sections was different in past papers from 2007 and earlier.
  • There are two practical papers. Paper 1 (3 hours) may include questions on mineral structures, igneous and metamorphic petrology. Paper 2 (1½ hours) and usually comprises a series of map interpretation questions followed by a related petrological exercise. All practical questions are compulsory. The practical exam counts for about 40% of the total marks.
  • The exam marking is done by a panel of three examiners, not necessarily staff who have taught the course in that year. Given the 60/40 ratio of theory to practical marks, each theory paper is scored out of 30% of the total marks, practical paper 1 is scored out of 26.7% and practical paper 2 out of 13.3%. No marks are awarded for missed questions. The raw total mark out of 100% is used to rank candidates by order-of-merit. The raw marks are then scaled (‘norm-referenced’) such that approximately 60% of candidates get a mark of 60 or above. The minimum marks for a pass, third, 2.2, 2.1 and first are 40, 50, 60 and 70 respectively. In a small subject cohort like IB Earth Sciences, there is some flexibility in these percentages and therefore in where examiners choose class borderlines. The examiners carefully scrutinise the marks of candidates close to borderlines, to ensure that you are awarded the subject class deserved by your exam performance.
  • You are then given a subject rank percentile (SRP) according to your ranking in IB Earth Sciences A. If r is your ranking (1 = top) and c is the class size, then your SRP is 100×(c+1–r)/c. So, if the class size is 50, then the person ranked top gets an SRP of 100, the second person 98, and so on down to the bottom person who gets 2. The SRP is used below in assigning your overall NST class.
  • The first estimate of your overall NST class is the median of your three subject classes. There is a table of all possible outcomes at www.natsci.tripos.cam.ac.uk/exams/marks-ib . A second measure is the arithmetic mean of your SRPs; candidates with an average percentile rank of ≥ 80% will be given a first, those between 80% and 40% a 2.1 and those between 40% and 20% a 2.2. Where the two methods produce different outcomes, you are placed in the higher of the two resulting classes.
  • Your College Director of Studies receives a breakdown of your marks into a theory and practical score for each subject.