How does QTAC do scaling in QCE?

Are all QCE subjects created equal? Should you choose subjects to please the scaling equation? Answers to these questions and more will be discussed below, so keep reading!

What is the ATAR?

As you may know, the ATAR ranges from 0.00 to 99.95 in 0.05 intervals. It is a percentile that ranks you against other ATAR students in the Grade 12 cohort of your state for the year you graduate. Each QCE subject has a total possible raw score of 100, and the best 5 subjects for each student are considered in the ATAR calculation.

There are two variable factors that influence the ATAR:

• The combination of the your top 5 subjects
• The performance of your state’s ATAR student cohort in the year you graduate.

Let’s break down how exactly these factors affect your ATAR.

What is Inter-subject scaling?

In QCE, there are over 50 subjects to choose from, meaning there is a huge number of subject combinations. This makes ranking students against each other challenging, since certain subjects may be easier to do well in than other subjects. Simply comparing students’ cumulative raw scores does not accurately reflect their academic ability.

This is where inter-subject scaling comes in.

Scaling is a method of objectively comparing raw scores from different subjects. It does so by converting raw scores into a common scale.

How are Subjects Scaled?

1. Initial scaled scores

A student’s raw score in a subject is used to rank them against all other students who took the same subject (even the ones not eligible for an ATAR).

2. Polyranks

A polyrank is the average of a student’s top five QCE subjects based on their scaled scores. This number is generated for all students.

3. Individual raw scores

A raw score achieved by an individual student in one of their top five QCE subjects is selected. This raw score is then used to find all the other ATAR students that scored that same raw score in that subject.

Once we have a pool of these specific students, their polyranks are averaged. This average becomes the next scaled score. This process of averaging polyranks of students who scored the same raw score in the same subject is repeated for every ATAR student’s top five QCE subjects.

4. Iterations

The scaled scores produced in step 3 cause student polyranks to change. Thus, this process of averaging the polyranks of students with the same raw scores in a subject will repeat until the estimated scaled scores start to stabilise, and each repetition has a negligible change in scaled scores.

Here's an example to illustrate:

This table illustrates how the raw scores of a hypothetical ATAR student are converted into scaled scores through iterations.

NOTE: The final iteration scaled scores are taken from QTAC’s Scaling report in 2021. The initial and first iteration scores are only estimated to illustrate how the scaled scores change with each iteration and should not be considered accurate.

As you might notice, this student scored the highest raw score possible in Dance, but this subject ended up having the worst scaled score in the final iteration of the scaling process. Thus, the scaled score for Dance would not be considered in their ATAR. Conversely, Modern History had the lowest raw score of 83 out of the six subjects, but its scaled score ended up being 87.43, which brings it up into this student’s top five QCE subjects based on scaled scores.

5. ATAR Calculation

Finally, ATAR is calculated by:

1. Filtering out students who don’t meet eligibility for an ATAR.
2. Then, a Tertiary Entrance Aggregate (TEA) is used to allocate students into ATAR bands.

The process of TEA is separate from scaling; you can read the QTAC report which outlines this process. This report also goes into more detail about the actual mathematical processes behind scaling and ATAR calculation in general.

How was QCE Scaled in 2021?

Now we’ll go into how to read the QTAC ATAR report, which you can find on the QTAC website. It has a lot of information about the cohort that graduated that year, as well as some more explanation about the ATAR, but most people are interested in how subjects are scaled, so let’s get into it!

Here are some quick facts about 2021’s subject scaling:

• The best scaling subject was Specialist Mathematics, with a raw score of 88 being equivalent to a scaled score of 97.78 (an increase of 9.78 points).
• The worst scaling subject was Dance, with a raw score of 100 being equivalent to a scaled score of 82.55 (a decrease of 17.45).
• A surprising scaling result came from Geography, which consistently scaled up (e.g. raw 84 scaled to 90). However, last year, it scaled down at its 99th percentile.
• English scales up generally (e.g. from a raw 77 to a scaled 84.57) but scales down when raw scores get higher (e.g. raw score of 97 is equal to a scaled score of 95.66).
• Literature follows a similar pattern to English, generally scaling up (e.g. raw 88 is scaled to 93.19) but scales down for higher scores (e.g. raw 99 is scaled to 96.99).
• Mathematical Methods scales up generously except for the 99th percentile, where a raw 99 scales to a 98.24 (which is quite a minor difference).

• Specialist Mathematics consistently scales up, where a raw 78 scales to 94.99 (an increase of 16.99 points).
• Economics consistently scales up, with a raw 96 scaling to 97.67.
• Physics generally scales up well (e.g. raw 89 scaling to 95.22) except for its 99th percentile which scales a raw 99 into 98.28.
• Chemistry consistently scales up, with a raw 94 scaling into a 97.25.
• Chinese consistently scales down, with a raw 100 scaling into 92.93.

Conclusion

In summary, scaling helps compare raw scores from different subjects in a fair way by converting them all into a common scale. This is done through a process of ranking students and averaging scores until final scaled scores are produced. The absolute amount that a raw score might scale up or down by changes every year, and it is not possible to accurately predict this.

It is highly recommended that you choose subjects that you genuinely enjoy, as this increases the likelihood of you studying well and ultimately performing well. There is no way to “game” the ATAR system, so just keep studying hard!

FAQs

Written by KIS Academics Tutor for QCE Mathematical Methods, Chemistry, Physics, Biology and Psychology, Hoi Yan Lee. Hoi is currently pursuing a Bachelor of Science Major in Psychology at UQ. You can view Hoi’s profile here and request her as a tutor.

If you’d like personalised, one-on-one help with your QCE studies, look no further! Explore KIS’s list of amazing QCE tutors who’ve been through the ATAR system with flying colours!