HSC Scaling Statistics

If you haven’t already done so, read how HSC scaling works.

Scaling statistics are published by the UAC each year. Scaled means of each subject are published in Table A3 and contains helpful information regarding how subjects scaled relative to each other for that year.

Scaling Statistics – learn how to read Table A3

Table A3 is a UAC publication released once a year that reports on the scaling statistics of all subjects used to determine all scaled marks and ATARs for the previous year. These statistics tell you everything about the scaling of all HSC subjects. These statistics are also used by ATAR calculators to work out ATARs given some subject marks.

Suffice to say, Table A3 is very useful!

How to read Table A3

In Table A3 there are always the same columns – luckily the UAC haven’t been changing the layout in past years.

columns of Table A3 scaling statistics

Things to notice

  • Course – the subject name (what else could it be!)
  • Number – the number of students taking it for that year
  • Type of mark
    • HSC mark is the aligned mark – read about the alignment process to find out more
    • Scaled mark is the important thing – it is the input for ATAR calculation – read about the scaling process to find out more
  • Mean – means average
    • The scaled mean tells us the average scaled marks achieved by students in that subject for that year. Mathematically, 25/50 is defined to be average so all subjects with an above 25 scaled mean have above average scaling and all subjects with below 25 have below average scaling.
  • SD – standard deviation – means ‘average spread of marks’. The higher the SD, the more spread out the marks. This is not too important for your purposes
  • Max. mark – this is the highest marks achieved among all students for that subject and year
  • P99 to P25 – these are important to understand. The P stands for percentile and the number is the percentile achievement needed to achieve the corresponding marks in that column. For example, to get the P99 mark, you need to be in the 99th percentile of the candidature for that subject / year – 99th percentile means out of 100 randomly selected students, you are first or second, or out of 1000 randomly selected students, you are tenth.

Examples on reading Table A3

Example 1: English Advanced vs Standard

Say it’s the end of year 10 and you need to choose your subjects for year 1 – you’re tossing between English Advanced and English Standard – a common conundrum! Looking at the scaling statistics of each, we see the below:

Example of reading Table A3 English Advanced vs Standard

From the above, you can see the P25 for English Advanced nets you 26.8 scaled marks (remember – scaled marks are what’s important as they are used for ATAR calculation!). To get around the same in Standard, you need to achieve higher than P75. This means a below average Advanced student in the 25th percentile (out of 100, he is coming 75th), he needs to be higher than the 75th percentile in Standard (out of 100, he is coming 25th) to get a similar result.

Example 2: Mathematics Extension 2

Scaling of Maths Extension 2

From the above you will notice:

  • Maths Extension 2 has a scaled mean of 43 in 2014 which is the highest amongst all commonly available subjects
  • A P25 result in Extension 2 is around a P80 in Mathematics (2 unit) and almost exactly the same as a P99 (top 1% achievement!) in Mathematics General II.

Quick Facts

  • In recent years, Maths Extension 2 was the highest scaled ‘mainstream’ subject (we are aware that occassionally some language subjects like Classical Greek Extension scales even higher).
  • Mathematics Extension 1 scales much stronger than English Extension 2.
  • Of the 3 sciences, Chemistry scales the highest, followed closely by Physics, then Biology.
  • Economics and English Advanced scale about the same as Physics and Chemistry.
  • Scaling statistics of individual subjects don’t tend to change significantly from year to year, so previous years’ statistics are a good indicator of the current or next years’.
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