As I previously mentioned, this year’s release of the Study Score Archive will feature estimated scaled scores alongside raw scores. Helpfully, VTAC provides scaling data in the annual Scaling Report, but correspondences between raw scores and scaled scores for each subject are provided only for scores that are greater than 20 and are multiples of 5 (that is, for the raw scores of 20, 25, 30, 35, 40, 45 and 50). As such, it is necessary to somehow estimate the correspondences for the remaining raw scores. This process in general is called interpolation.
A simple method of interpolation is linear interpolation. This is the approach used by Daniel15’s VCE ATAR Calculator, and it is the approach that I will be using in the 2010 release of the Study Score Archive. Other methods might produce more accurate results, but they are harder to implement and without more data it’s not possible to verify which method of interpolation produces the best results.
To illustrate the process, let’s take a look at the scaling of Further Mathematics in 2010 (for scores of 40 and above).