[Catalist] Chemistry mark distribution

[Leon Harris]

Greetings to all !

I have been puzzling over the marks distribution for year 12 WACE 2018 
for Chemistry. You can find the data I am looking at is published here: 
https://senior-secondary.scsa.wa.edu.au/__data/assets/pdf_file/0011/549848/2018_CHE_ATAR_course_summary_examination_report.PDF


"That's not normal !" doesn't cover it for me. I think I can identify 3 
clear populations in that one, supposedly normally distributed graph.

So then the interesting questions that arise are: 1) What are those 3 
populations, 2) Are they present in the same proportion for all schools, 
and 3) What effect do they have on grade scaling in ATAR score calculation.


I'd hazard a guess: the first one with a mean centred around 33% is 
probably the group of kids who have given up. "Nah, got 4 ATAR, Chem is 
too much study, got to show up to the exam so I graduate but that is 
about all I will do"

The interesting thing is what distinguishes the next two (mean =51, and 
mean = 67)?

What do you guys think?
If I get time I might toddle over to physics and human bio to see if the 
pattern is similar there, and maybe compare against English or Lit which 
has a more compulsory nature.


Penny for your thoughts !

Cheers,

Leon



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