Scaling and the ATAR

The Australian Tertiary Admission Rank (ATAR) is a percentile ranking used by universities to assist in the selection of school leavers for entry into undergraduate courses. It is used as an indication of a student's suitability for study at university level, and to allow universities to select appropriate numbers of students for each course. The ATAR is a ranking of a student relative to the full age cohort i.e. relative to the set of students who would be in the group if all students stayed on and completed Year 12. It is reported with a range from 99.95 for the highest ranked students down to 30.00. For example, a student with an ATAR of 85.00 indicates a performance better than 85% of the population eligible to be in Year 12 or in the top 15% in relation to all the students who started school at the same time.

In the ACT, the ATAR is reported on the Tertiary Entrance Statement. A Tertiary Entrance Statement is produced for each student who meets the requirements set down by the ACT Board of Senior Secondary Studies for eligibility to apply for entry to university.

Step 1: Course scores

Colleges calculate a course score for each student in each T or H course from their best 80% unit scores. A course score indicates how well a student performed in a particular course compared to all other students in that course's scaling group at the college. A scaling group is the group of students completing T or H courses in a particular area. The students may all have completed the same course, or they may have completed different courses. For example, a college may group students from their Accounting and Business Studies courses in a single scaling group. This will allow course scores for those courses to be directly compared. Course scores are not percentages and typically lie between 30 and 105.

Step 2: Scaling

So that scores from different scaling groups and colleges can be compared the course scores need to be placed on a common scale. In the ACT, a process called Other Course Score (OCS) scaling is used to adjust course scores to bring them to a mean and standard deviation related to the student's performance in their best 4 course scores and the ACT Scaling Test (AST).

The scaling procedure changes the score used to represent each student's rank in a particular scaling group, but it does not alter the ranking of students or the shape of the distribution. For example, if Student A is above Student B in Economics, Student A will still be above Student B after scaling.

Step 3: Using scaled scores to produce an Aggregate Score

Once course scores are scaled, they can be added to form an Aggregate Score. The Aggregate Score is the number produced by adding the best three scaled scores from major courses, and 0.6 of the next best course score (either major or minor).

Step 4: Calculating the ATAR

The Aggregate Scores for all students who have met the requirements are listed in order from highest to lowest. This ranking is then converted to an age rank (ATAR) by using a table supplied by the NSW Technical Committee on Scaling. This gives a rank for ACT students as if they were part of the NSW age cohort. The ATAR calculated in the ACT is directly comparable to the ATAR calculated in NSW and the same entrance cutoffs at NSW and ACT universities apply to both NSW and ACT students. If you are applying to interstate universities, state admission centres will use the ATAR for entry to their universities. This means that interstate applicants will be able to directly compare their ranks with university entrance cut-offs irrespective of their state of origin.

Briefly, the stages in the process are:

  1. For each student, a measure of General Achievement (GA) is calculated by adding 0.8 of her/his AST score and best 3.6 course scores. The course scores from the best 3 T majors and the next best T course score – either major or minor – are used.
  2. The average and the spread of the GA scores in each scaling group are calculated, and the course scores are then adjusted so that they have the same average and spread as the GA scores.
  3. The AST and the adjusted course scores are used to calculate revised GA values.
  4. The course scores are adjusted again (as in step 2) using these revised GA values. The process continues working through steps 3 and 4 until the adjustments made to the course scores from one step to the next are no longer significant. In practice this usually takes less than twenty cycles.