How do you calculate what 'top percent' your study score is?

[perpetual]

I know that a 40 is top 9%, 45 is top 2% for the subjects with a high intake, but I need to find out the exact 'top %' of my 47 and 48 study scores from last year. Does anyone know how to calculate that?
Thanks.

[vox nihili]

I know that a 40 is top 9%, 45 is top 2% for the subjects with a high intake, but I need to find out the exact 'top %' of my 47 and 48 study scores from last year. Does anyone know how to calculate that?
Thanks.

http://stattrek.com/online-calculator/normal.aspx

Normal random variable (x)= [enter your score]
Cumulative probability: P(X < 40)= [enter nothing...this'll be your result!]
Mean= [see below]
Standard Deviation= [see below]

For the value of the mean and standard deviation, access the VCE scaling report: http://www.vtac.edu.au/pdf/scaling_report.pdf These values are in the second and third columns respectively.
Note: you can only do these for raw scores
Also note: the website may start off by saying "Normal Random Variable (z)". It will change to x once you've entered different values for mean and standard deviation.

[vox nihili]

I had to do a bit of back working from below, since just using a normal distribution with mean=30 and standard deviation=7 didn't give the below.
http://www.vcaa.vic.edu.au/pages/faqs/vcecurrentstudents.aspx
The following seems to work, if you want to know , then find using a normal distribution with mean=30 and standard deviation=7.

Since you don't have methods in your sig, try this link http://www.wolframalpha.com/input/?i=Pr%28X%3E45-0.5%29%2C+normal+distribution%2C+mean%3D30%2C+sd%3D7
BUT replace the 45 with your scores, and remember this is only an approximate figure.
So for 47 and 48 we have top 0.92% and 0.62%.

http://www.wolframalpha.com/input/?i=Pr%28X%3E47-0.5%29%2C+normal+distribution%2C+mean%3D30%2C+sd%3D7
http://www.wolframalpha.com/input/?i=Pr%28X%3E48-0.5%29%2C+normal+distribution%2C+mean%3D30%2C+sd%3D7
Just so that everyone else doesn't go off at me and say that it's not right, here is the calculation to each example given from the VCAA website using this method. It seems to work since you can only get a discrete study score, and not halfway between integers.
http://www.wolframalpha.com/input/?i=Pr%28X%3E45-0.5%29%2C+normal+distribution%2C+mean%3D30%2C+sd%3D7

http://www.wolframalpha.com/input/?i=Pr%28X%3E40-0.5%29%2C+normal+distribution%2C+mean%3D30%2C+sd%3D7

http://www.wolframalpha.com/input/?i=Pr%28X%3E35-0.5%29%2C+normal+distribution%2C+mean%3D30%2C+sd%3D7

http://www.wolframalpha.com/input/?i=Pr%28X%3E30-0.5%29%2C+normal+distribution%2C+mean%3D30%2C+sd%3D7

http://www.wolframalpha.com/input/?i=Pr%28X%3E25-0.5%29%2C+normal+distribution%2C+mean%3D30%2C+sd%3D7

http://www.wolframalpha.com/input/?i=Pr%28X%3E20-0.5%29%2C+normal+distribution%2C+mean%3D30%2C+sd%3D7

In reality, the standard deviation and the mean never end up being exactly 7 and 30 respectively. Makes it a bit confusing when they specifically say what you've quoted. They underestimate who is actually interested in that rubbish! hahah

[b^3]

Yeah I know, I forgot that we get the individual means and standard deviations for each subject... I've been out of this for a while

[lala1911]

Percentages of how many people get each study score!

[vox nihili]

Yeah I know, I forgot that we get the individual means and standard deviations for each subject... I've been out of this for a while

I got half way through it and thought, shit...this is all wrong! I don't think that calculating study scores is the pinnacle of mathematical knowledge though, so we're safe! haha

[Professor Polonsky]

I don't think you need to grab the mean and sd from the scaling report. This is the mean and sd of the scaling cohort of that subject in their other subjects (essentially, the distribution of scaled scores).

bcub3d's (previously deleted, now reposted below) post, and the post Lala linked to, are as accurately as we can predict the distributions.

[b^3]

Now that I look back at it, that seems correct.

I'll just put the post back here then.
I had to do a bit of back working from below, since just using a normal distribution with mean=30 and standard deviation=7 didn't give the below.
http://www.vcaa.vic.edu.au/pages/faqs/vcecurrentstudents.aspx
The following seems to work, if you want to know , then find using a normal distribution with mean=30 and standard deviation=7.

Since you don't have methods in your sig, try this link http://www.wolframalpha.com/input/?i=Pr%28X%3E45-0.5%29%2C+normal+distribution%2C+mean%3D30%2C+sd%3D7
BUT replace the 45 with your scores, and remember this is only an approximate figure.
So for 47 and 48 we have top 0.92% and 0.62%.

http://www.wolframalpha.com/input/?i=Pr%28X%3E47-0.5%29%2C+normal+distribution%2C+mean%3D30%2C+sd%3D7
http://www.wolframalpha.com/input/?i=Pr%28X%3E48-0.5%29%2C+normal+distribution%2C+mean%3D30%2C+sd%3D7
Just so that everyone else doesn't go off at me and say that it's not right, here is the calculation to each example given from the VCAA website using this method. It seems to work since you can only get a discrete study score, and not halfway between integers.
http://www.wolframalpha.com/input/?i=Pr%28X%3E45-0.5%29%2C+normal+distribution%2C+mean%3D30%2C+sd%3D7

http://www.wolframalpha.com/input/?i=Pr%28X%3E40-0.5%29%2C+normal+distribution%2C+mean%3D30%2C+sd%3D7

http://www.wolframalpha.com/input/?i=Pr%28X%3E35-0.5%29%2C+normal+distribution%2C+mean%3D30%2C+sd%3D7

http://www.wolframalpha.com/input/?i=Pr%28X%3E30-0.5%29%2C+normal+distribution%2C+mean%3D30%2C+sd%3D7

http://www.wolframalpha.com/input/?i=Pr%28X%3E25-0.5%29%2C+normal+distribution%2C+mean%3D30%2C+sd%3D7

http://www.wolframalpha.com/input/?i=Pr%28X%3E20-0.5%29%2C+normal+distribution%2C+mean%3D30%2C+sd%3D7

[vox nihili]

This is true! Sorry bˆ3 and everyone else, looks as though I was wrong

Gotta love those moments. "Ohhh no, you've got to take this exception" *feel really smart*..."you actually don't need to at all"...."oh"

And this I daresay is exactly why you're doing Eng and I'm not! haha

[Lasercookie]

So more or less, t-rav's method will be for scaled study scores in a specific year, whilst b^3's method would be for raw study scores? The difference between the two being whether you're taking the mean of 30 and std. dev of 7, or the ones from the VTAC scaling report (though taking the intervals of .5 as b^3 stated?)

[b^3]

So more or less, t-rav's method will be for scaled study scores in a specific year, whilst b^3's method would be for raw study scores? The difference between the two being whether you're taking the mean of 30 and std. dev of 7, or the ones from the VTAC scaling report (though taking the intervals of .5 as b^3 stated?)

I think t-rav's method would work given the scaled score, I wonder how close the two values would be.