How was the exam? (2 Viewers)

[~ ReNcH ~]

Rench: how did you calculate that. Your numbers seem (VERY) flawed.

Yep, I've wondered that myself and I admit that it seems crazy. Anyway, this is from a PM I just sent ||! explaining how I got the result:

Aligned marks are determined by linear interpolation, in other words you basically have two end-points on a cartesian plane and draw a line between them, and so you then "fill in the gaps".

Now, suppose 40/120 --> 90 and 120/120 --> 100 (the last end-point is always 100%).
Now we represent them as points on a plane:
A(40, 90) and B(120, 100) - where "x" is the raw mark /120 and "y" is the corresponding aligned mark /100.

The equation of AB: y = (x + 680)/8

Try substituting Keypad's raw mark of 108/120 into the equation and you get y = 98.5 which rounds to 99. Obviously, if the cut-off were >40 or Keypad got <108, his aligned mark would have been <98.5 and that wouldn't have rounded to 99. But he got 99, so the cut-off must be <40/120 unless Keypad actually got >108/120 raw.

If you can find an error in my working, then please point it out but I've gone through it a few times and I can't find anything wrong with it.

 

[Estel]

How do you know aligned marks are determined by linear interpolation over sets of 10?

 

[~ ReNcH ~]

How do you know aligned marks are determined by linear interpolation over sets of 10?

I asked Laz. It seems like the only logical way to do it anyway, seeing as there are no "standards" for aligned marks mid-way between Band cut-offs. The aligning committee has to stick to the band descriptors and given that there aren't any published for aligned marks of 95 or 85 etc. then it's the only way that it could be done.

 

[Vinniejaa]

I asked Laz. It seems like the only logical way to do it anyway, seeing as there are no "standards" for aligned marks mid-way between Band cut-offs. The aligning committee has to stick to the band descriptors and given that there aren't any published for aligned marks of 95 or 85 etc. then it's the only way that it could be done.

I seem convinced abt the linear interpolation theory but do u know how they determine the cut of for 90 +. I mean, 40/120 seems too low. wudnt it be more like 70/120. Coz using yur formula, if i got 80/120 yesterday, equates to 95 which seems too high for 80/120. what do u personally reckon 80/120 wud get u considerin 83/120 ~93 last year and that this year was harder.

 

[tofu]

I seem convinced abt the linear interpolation theory but do u know how they determine the cut of for 90 +. I mean, 40/120 seems too low. wudnt it be more like 70/120. Coz using yur formula, if i got 80/120 yesterday, equates to 95 which seems too high for 80/120. what do u personally reckon 80/120 wud get u considerin 83/120 ~93 last year and that this year was harder.

his 'formula' was based on 2003... who says it's applicable to 2005?

 

[Dumsum]

Do they do each interpolation for separate bands or all as one? Because using Rench's formula, if you get 0/120 you get 85 aligned

I just came up with something now, using a small bit of data and a quadratic rather than linear approach.

0/120 -> 0/100
108/120 -> 99
120/120 -> 100

Using that I came up with y = -0.0069x^2 + 1.6667x. So a raw mark of 80 will get you aligned of 89.

I dunno. It's likely I have no idea what I'm doing, but this seems more fair although maybe not fair enough.

 

[ishq]

33% -------------------------> 90%
I thought it was a bit far fetched.

 

[justchillin]

Lol where did u pull that formula from mate... seems 2 work though

 

[~ ReNcH ~]

Do they do each interpolation for separate bands or all as one? Because using Rench's formula, if you get 0/120 you get 85 aligned

I just came up with something now, using a small bit of data and a quadratic rather than linear approach.

0/120 -> 0/100
108/120 -> 99
120/120 -> 100

Using that I came up with y = -0.0069x^2 + 1.6667x. So a raw mark of 80 will get you aligned of 89.

I dunno. It's likely I have no idea what I'm doing, but this seems more fair although maybe not fair enough.

BOS determines the cut-off for a Band E4, E3, E2 and then interpolates the marks between each. So if the cut-off for E4 was 70/120 and for E3 it was 50/120, then for raw marks falling between 50 and 70/120 the two end-points are 50 and 70...they don't continue the E4 linear function all the way to a raw mark of 0/120 coz I'm pretty sure 0 --> 0. Afaik, they don't use a quadratic formula.

They would never use (0,0) and (120,100) as the end-points as that would defeat the purpose of having separate bands. I know it seems ridiculous that the Band E4 cut-off could be 40/120 (even I'm worried by it), but unless someone can prove my working incorrect or can find out a definitive answer to whether they linearly interpolate the marks or not, then I can't say otherwise.

Edit: http://www.boardofstudies.nsw.edu.au/hsc/hsc_update_2002_06.html

It explains it all here.

 

[Dumsum]

BOS determines the cut-off for a Band E4, E3, E2 and then interpolates the marks between each. So if the cut-off for E4 was 70/120 and for E3 it was 50/120, then for raw marks falling between 50 and 70/120 the two end-points are 50 and 70...they don't continue the E4 linear function all the way to a raw mark of 0/120 coz I'm pretty sure 0 --> 0

Hmm yeah thought that might have been the case. Thanks for the link...

"Once the cut-off marks are approved by the HSC Consultative Committee, the cut-off examination mark between Band 5 and Band 6 is assigned a value of 90. The cut-off mark between Band 4 and Band 5 is assigned a value of 80; between Band 3 and Band 4, a value of 70; and so on. A raw mark of 100 is assigned a value of 100, and a mark of 0 a value of 0. Examination marks between the cut-off marks are then allocated in a linear manner."

With that in mind...I'm inclined to agree with you.

Man, it'd be awesome if it's around 40 this year...I'd be stoked to get mid 90s lol.

 

[~ ReNcH ~]

No probs. It does seem odd that the cut-off could be so low, but from the data that I have (and it seems like conclusive data), I can't come to any other conclusion - that said, I hope there's nothing wrong with my linear equation.

To be safe, I'd say 65-72/120 but who knows? It'd be nice if it was 40/120 though

 

[Estel]

Then that leaves two things:
Keypad didn't get 108; OR
Keypad didn't get 99 aligned.

 

[Vampire]

how can he be so certain he got 108/120?

 

[~ ReNcH ~]

Then that leaves two things:
Keypad didn't get 108; OR
Keypad didn't get 99 aligned.

Well, he must have got 99 since the highest mark was 99 according to the UAC data - unless he got an assessment mark of 100 and an exam mark of 98, though he was probably first at school meaning that that isn't the case.

And he told me that he didn't put pen to paper for 12 marks, so 108/120 is the most he could have got.

 

[~ ReNcH ~]

how can he be so certain he got 108/120?

From a PM he sent me:

and yes, I physically didn't answer 12 marks worth of questions. Pen was not put to paper for them.

 

[Vampire]

hmmm i see, but this is 2003, which is generally considered harder than this years...so a band e4 cut off might be closer to 50-60?

 

[~ ReNcH ~]

hmmm i see, but this is 2003, which is generally considered harder than this years...so a band e4 cut off might be closer to 50-60?

I'd say 65-75 to be safe, but it's better to be conservative. If it turns out to be lower, then we'll be pleasantly surprised

 

[Vampire]

that's still cool...(quite a big jump from 03 to 05)

 

[Estel]

Well we make the assumption that 120/120 is required to get 100. Is this warranted? (i.e. is this in writing anywhere?)

 

[ishq]

Well, he must have got 99 since the highest mark was 99 according to the UAC data - unless he got an assessment mark of 100 and an exam mark of 98, though he was probably first at school meaning that that isn't the case.

And he told me that he didn't put pen to paper for 12 marks, so 108/120 is the most he could have got.

What about something he got WRONG?