Considering Adelaide has a very high decline rate (as a lot of interstate applicants who gets an offer would probably get a home-state offer as well), wouldn't that mean the offer to interview ratio can potentially be around 1 in 3? (originally 130 places for 600 interviews is around 1:4.5). Assuming someone has a maximum ATAR (worth 40%) and top 0.1%ile UCAT(worth 20%), the combined score of 60% would be the maximum score (One of my friend's parent is involved in the admission team of Adelaide med and he said that Adelaide uses a Z-score distribution for each component score), which would mean that regardless of the number of people with "adjusted" 99.95, the applicant with a top UCAT score and ATAR would still be on the top of the list due to the Z-score. Overall to get an offer, wouldn't that mean ending up with a 250ish position out of the 600 applicants who received an interview would be sufficient? (also taking into consideration of the 50% SA interview sub-quota, meaning that the majority of the 300 SA applicants would have a significantly lower UCAT score, further pushing the advantage?). Thus, in the interview component, having an average score would be sufficient to not drag down the overall score to the bottom 50%? As the applicant would have a maximum ATAR + UCAT score? Sorry about lengthy post HAHAHA just some random thoughts!
EDIT: And also not everyone with a killer interview would also have a raw/adjusted 99.95 or/plus top UCAT, as everyone can have different strength and weaknesses. (It is def possible but this will not be the case for the majority of the offers from Adelaide med considering some people I know got in with a 99ish ATAR, ~2800 UCAT)
And considering your case
A1 it could potentially be due to the fact that Adelaide has not yet introduced the interview sub-quota, hence it is harder to get a big advantage on the UCAT section over the SA applicants?
Adelaide *used* to have a high decline rate as you said due to literally 80% of the interviewees being from interstate, in my year I remember knowing like 5 people on the list of people who got a first-round offer, but following subsequent offer rounds, basically everyone I knew who interviewed ended up getting a top-up offer. As a result, the Adelaide cohort still predominantly consists of SA students.
You can tell how lopsided the interview demographic was by looking at what happened to the interview cutoffs after Adelaide introduced a 50% subquota for SA students last year:
2019: 91%ile for everyone
2020: 71%ile for SA students, 96%ile for interstate students.
The decline rate might've gone down last year after Adelaide started interviewing more SA students.
With reference to z-scores, that's not how z-scores work. Z-scores are not out of 1 and aren't like percentiles either. They refer to standard deviations above and below the mean. What it means is that if your UCAT score is astronomically high, you're basically leaps and bounds ahead of everyone else. Take this scenario of 16 students for example:
Students 1-5: 2900 UCAT
Students 6-10: 3000 UCAT
Students 11-15: 3100 UCAT
Student 16: 3500 UCAT
Mean: 3031.25
Standard deviation: 144.56
Students 1-5:
-0.98 z-score (i.e. 0.98 standard deviations below the mean)
Students 6-10:
-0.22 z-score
Students 11-15:
0.48 z-score
Student 16:
3.24 z-score (WTF)
As you can see, student 16, by virtue of getting a 3500 UCAT score, has basically eliminated the competition in the z-score department. There is literally no way for the other students to catch up, with students 1-5 literally falling over 4 standard deviations behind student 16. Z-scores are scary for components like the UCAT where there is a lot of potential to open up the lead between yourself and the person in second place - 3300 and 3600 are both technically considered 99%ile, but the latter basically doubles your competitiveness. The same is not true for ATAR, where everyone clusters around the 99 mark and so even if you did get a 99.95 ATAR, so did tens of other people and if not 99.95, then 99.90.
This is why I doubt that Adelaide uses z-scores because it disproportionately benefits UCAT, and as we've seen before, a stellar UCAT can't compensate for a less-than-stellar interview. They more likely use a ranking system, where the highest UCAT score is attributed a rank of 1, the second highest a rank of 2 etc. Then, your rankings in each of the components are multiplied by the weightings and added together (e.g. (50th x 0.2) + (100th x 0.4) + (150th x 0.4)). Everyone's combined score is once again rearranged from lowest to highest, with the lower the better. Adelaide then gives the top 150 people place offers. The quirk of using a ranking system is that it eliminates the gross advantage of a 3500 UCAT score over a 3300 - it would give the 3500 a rank of "1" and 3300, say, a rank of "5". Not much advantage to be had there. Drop 2 places in your interview ranking (worth double) and you've lost your lead.