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# How do grade boundaries get decided? Watch

1. I completely understand the fact that there is a UMS scale at which raw marks are converted to reflecting overall student's performances on a paper. But is there any sort of algorithm to how they come to be?
Is it something as simple as the top 10% get an an A* for example? Or do they work out what they assume and A and an E to be and then divide by 5 to get the difference between grades?
If anyone has any inclination to their actual process of generating the UMS scale please let me know!
2. (Original post by cowie)
I completely understand the fact that there is a UMS scale at which raw marks are converted to reflecting overall student's performances on a paper. But is there any sort of algorithm to how they come to be?
Is it something as simple as the top 10% get an an A* for example? Or do they work out what they assume and A and an E to be and then divide by 5 to get the difference between grades?
If anyone has any inclination to their actual process of generating the UMS scale please let me know!
I believe they mark all of the countries papers for a set exam first. They then look at the results and calculate the grade boundaries so that, from the people who took the paper, the top certain % of people get A*s As Bs etc.

So the grade boundaries are set afterwards to ensure the correct percentage of people get the grades exam board wants them too.
3. That's why it's not bad if everyone does bad in an exam.... because if literally everyone did, then an A* would be something like 50% marks :P
4. UMS Calculator for AQA: http://www.aqa.org.uk/exams-administ...t-marks-to-ums

It's basically a system that adjusts your raw marks in accordance to the difficulty of the paper. The adjusted marks (UMS) are then used to calculate your grade (e.g. 160/200 UMS for an A). As far as I know, with the exception of IB, the top mark(s) is/are not allocated on the basis of a proportion (say, A* being the top 5% of candidates or whatever).
5. I was told that there was a standard deviation type curve that they use to calculate it. If that's true, how would skewness affect grade boundaries?
6. (Original post by emerl98)
I was told that there was a standard deviation type curve that they use to calculate it. If that's true, how would skewness affect grade boundaries?
For AQA, and I imagine for the other exam boards as well, UMS is awarded almost proportionately to your raw mark, and often comes to a plateau/ grade cap where a raw percentage that is less than 100% will give you full UMS. It's not exactly linear, but the curve on the graph line is so small that it has a tiny effect on your UMS in reality (as long as you don't get like 15% raw marks or something stupid).

Take a look at the UMS Calculator I linked above - put in some random subjects and dates, and then take a look at the graph it produces.
For example: image
7. (Original post by JohnGreek)
For AQA, and I imagine for the other exam boards as well, UMS is awarded almost proportionately to your raw mark, and often comes to a plateau/ grade cap where a raw percentage that is less than 100% will give you full UMS. It's not exactly linear, but the curve on the graph line is so small that it has a tiny effect on your UMS in reality (as long as you don't get like 15% raw marks or something stupid).

Take a look at the UMS Calculator I linked above - put in some random subjects and dates, and then take a look at the graph it produces.
For example: image
I get the original idea of how UMS is calculated. But how do they decide the raw mark boundaries that contribute to a particular grade in a subject? I know that raw mark boundaries are calculated in relation to how the rest of the country. But what is the method used to do so?

I heard the boundaries were calculated using a normal distribution curve. If so, then I assume that the mean mark would be a C grade. And how would skewness affect results?

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