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# Arsey's S1 Edexcel Summer 2013 Model Solutions BOTH PAPERS watch

1. (Original post by JinxedOut)
For 4f) I just wrote reduced (left out by five), how many marks would that be likely to lose (I got whether they reduced or stayed the same right)? For 1c) I also wrote yes, lie close to a straight line, and on the venn diagram I thought the 0s wouldn't be necessary. They're the only mistakes I made according to this mark scheme and thread, I need 84 UMS so fingers crossed.
I don't think it matters if you left out the zero- technically you would have got all the marks providing the values are correct.

If the examiners aren't too harsh you should get away with the "lie close to straight line" if you haven't written about r is close to -1 (or you would only lose one mark max for this)

For 4f if you've written which ones reduce by 5 or stay the same correctly it should get you all three marks. ( sorry didn't understand what you meant for 4f)

Overall you've done pretty amazing! :-)
2. (Original post by JinxedOut)
For 4f) I just wrote reduced (left out by five), how many marks would that be likely to lose (I got whether they reduced or stayed the same right)? For 1c) I also wrote yes, lie close to a straight line, and on the venn diagram I thought the 0s wouldn't be necessary. They're the only mistakes I made according to this mark scheme and thread, I need 84 UMS so fingers crossed.
Ok sorry just understood what you meant. Errrmmm for the 5 bit that you left out.. It's already written in the question about decreasing by 5. I'm sure it won't be that big of a deal for missing out 5 . If you've written that the standard dev stays the same you should definitely get a mark for that which I'm sure you will.
3. (Original post by Eviey)
Ok sorry just understood what you meant. Errrmmm for the 5 bit that you left out.. It's already written in the question about decreasing by 5. I'm sure it won't be that big of a deal for missing out 5 . If you've written that the standard dev stays the same you should definitely get a mark for that which I'm sure you will.
I hope we get the mark for lie close to a straight line. I mean we obviously wrote that because we knew r was -0.95
4. (Original post by Xx4L3x)
I hope we get the mark for lie close to a straight line. I mean we obviously wrote that because we knew r was -0.95
Well in the past mark schemes they give you a mark for saying that so hopefully it applies here too (Y)
5. (Original post by Eviey)
I don't think it matters if you left out the zero- technically you would have got all the marks providing the values are correct.

If the examiners aren't too harsh you should get away with the "lie close to straight line" if you haven't written about r is close to -1 (or you would only lose one mark max for this)

For 4f if you've written which ones reduce by 5 or stay the same correctly it should get you all three marks. ( sorry didn't understand what you meant for 4f)

Overall you've done pretty amazing! :-)
Thanks for the response! I hope you're right/ marking my paper.. You never know how picky they'll be, you can get every answer technically right but lose silly marks for missing key words. I concentrated so hard on that damn venn diagram I am just thankful that I worked something sensible out in the end
6. (Original post by Mr M)
Is Graham a revered and legendary character in Edexcel A Level threads? I've met him. Can I claim a prize?
your sure can claim a prize apparently he is a revered and legendary character, but how have u met him if you don't do the EDEXCEL syllabus you do OCR right??? [how hard is OCR M2]
7. (Original post by JinxedOut)
Thanks for the response! I hope you're right/ marking my paper.. You never know how picky they'll be, you can get every answer technically right but lose silly marks for missing key words. I concentrated so hard on that damn venn diagram I am just thankful that I worked something sensible out in the end
Yep that's true. They can be picky. It's good the Venn diagram worked out well for you since that was worth quite a few marks. Good luck with the rest of your exams!
8. (Original post by MAD Phil)
None.

Venn diagrams can show the actual elements in each section, the number of items, or, (in the context of probability), probabilities.

Which is best depends on context, or any explicit instructions. Here you weren't given any explicit instructions, but the subsets were referred to as "events", putting the question in a probability context. So giving probabilities as you did is certainly appropriate. I would be outraged if you lost a mark.

In fact, I think it is more likely that people who did what Arsey and I did would lose a mark for not picking up on the word "event", but I think that is still very unlikely. Almost certainly either choice will get full marks.
.

i drew three circles obviously with wrong values do you think i will get a 1 mark
9. (Original post by Fas)
Aslong as you had the events F , H and C all intersecting ( overlapping ) with the event B , BUT F , H and C didn't overlap each other then your correct

thats what i did anyway - did one big circle for event B , then had the other three circles intersecting the big circle , but the other three did not intersect each other.
I'm afraid that's very unlikely to be enough for full marks, because it doesn't show that {F, H, C} is a partition, i.e. that the three sets do not overlap, but together make up all the space.

You need to either draw those three sets so that they take up the whole of the rectangle, or explicitly show that there is nothing outside them by putting in the two zeros. (I much prefer the former option, because the later is inconsistent; it shows some empty areas of the diagram are empty by making them non-existent, and others by labelling them as empty.)
10. (Original post by Arsey)
It doesn't mean that, it is NOT full time AND walks. Think about what that would look like on a Venn. You have to also include full timers who don't walk and walkers who are not full time.

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Arsey, if i did not include the zeros in the venn diagram how many marks will i lose if any? I thought it wouldve been implied

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11. (Original post by TheKingOfTSR)
Anyone knows or would confirm whether question four was positively or negatively skewed?
Both!

The idea of skewness only really makes unequivocal sense for "nice" distributions. Various different ways of measuring skewness have been developed which will broadly agree for such nice distributions, but when you apply them to distributions which aren't particularly nice, they often don't agree.

I had some fun once creating a spreadsheet that would create a new set of random data each time you pressed a particular key, It would then produce a histogram, box-plot etc, and would calculate whether the data was positively skewed several different ways - comparing mean with median, median with mode, mode with mean, Q3 - Q2 with Q2 - Q1, and Q4 - Q3 with Q1 - Q0. My students were amazed how rare it was for all 5 tests to agree about whether the data was positively or negatively skewed.
12. I hope I get an A , i didnt want histograms to come up because I could do EVERYTHING else and I go and mess up the paper, so if I resit next year Ill probably do worse and therell probably be a histogram question.

Low grade boundaries please (Wont happen _)
13. For the Venn Diagram one, I worked out the percentages of each amount. WIll I get a mark?
14. (Original post by TheGoldenRatio)
MAD Phil firstly great solutions like the Notes, secondly im sorry to say your hand writing is atrocious
Thanks! Sorry about the handwriting, but I'm not going to get out of bed and use a desk just so people can read it! Just be grateful it's not my head of department posting - people get used to my writing in time, but I still can't read his after 20 years.
15. (Original post by Mr M)
Is Graham a revered and legendary character in Edexcel A Level threads? I've met him. Can I claim a prize?
Have you seen the video of him sitting while a sculptor makes a bust of him, pigtail and all? I can't remember exactly where it is, but I think we found it by rummaging around in the Emporium somewhere.

As Arsey says, he's a good guy and deserves his weekend off!

I particularly like the dry humour in some of the documents he sends out. A while ago, I was chuckling away at an email attachment that I thought had come from my HoD, when I was astonished to notice it was actually an official Edexcel document from Graham.
16. (Original post by Arsey)
Centres are allowed to use papers for internal use once all of their candidates have sat the paper no idea what your exams officer is on about. In the good old days I could go in just before the exam have a good shufty through the paper.

I am no Edexcel mole. I have used pretty much every centre over the years and without question Edexcel are the most professional and offer the most support. GC is a very nice bloke too. That said, I am more than happy to criticise them when merited. I am not sure what you mean by individualistic either.

There is an option in acrobat pro to reduce file sizes btw.
Hi Arsey, glad to meet you. Thanks for the info about the use of exam papers; perhaps I'll try to push for a change of policy at our place. As you say, things have tightened up compared to the good old days, but it sounds as if they are a lot tighter here than elsewhere. We had assumed that that was because of rules coming from Edexcel reflecting the use of the exams across time-zones, but if it's just empire-building closer to home, your information will be useful and much appreciated in the fight-back!

By being "individualistic" I guess I just mean "out of line with sensible mathematical practice", or, roughly speaking, "Wrong". This seems to happen mainly in S1, which is why I don't like teaching it. At our college we have quite a collection of what we call "Edexcel shibboleths", i.e. things that students have got to say to get marks from the S1 examiners, even though they are unjustified or just plain wrong.

Some of us hold our noses and try to teach S1 the Edexcel way, pretending to believe in the shibboleths ourselves. Others teach what they believe is logical, sensible and correct, and then explicitly warn the students about the shibboleths, drumming it into them just before the exam that it's worth writing what you know the examiner wants, even though you know it's not true.

Both strategies have advantages and disadvantages. Personally I go for the second, but I can completely see why some people go for the first, and I completely respect that decision.. I just think it's very unfortunate that Edexcel forces the choice on us.

Sorry if I came over as a bit brusque in my first posting; no offence was intended, and I really hope none was taken. Now it's 3.10 a.m, and I really think I must go to sleep before I put my foot in it again.
17. I thought this paper was harder than the Jan 2013 in my opinion... Well done to me, I've completely messed up the N Distribution question (I couldn't seem to think straight) and some of the probability:/
Ahh well, at least, somehow, I'm better at S2 XD
18. (Original post by Xx4L3x)
I think they are looking for the actual % though
You are missing the point. Percent is a measure of 100. That is what it means.

2.74% is defined as 2.74/100 which is 0.0274.

They might very well deduct a mark for it but they really shouldn't. The question is designed to test knowledge of normal distribution which is why it would be daft to penalise this.

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19. (Original post by MAD Phil)
Hi Arsey, glad to meet you. Thanks for the info about the use of exam papers; perhaps I'll try to push for a change of policy at our place. As you say, things have tightened up compared to the good old days, but it sounds as if they are a lot tighter here than elsewhere. We had assumed that that was because of rules coming from Edexcel reflecting the use of the exams across time-zones, but if it's just empire-building closer to home, your information will be useful and much appreciated in the fight-back!

By being "individualistic" I guess I just mean "out of line with sensible mathematical practice", or, roughly speaking, "Wrong". This seems to happen mainly in S1, which is why I don't like teaching it. At our college we have quite a collection of what we call "Edexcel shibboleths", i.e. things that students have got to say to get marks from the S1 examiners, even though they are unjustified or just plain wrong.

Some of us hold our noses and try to teach S1 the Edexcel way, pretending to believe in the shibboleths ourselves. Others teach what they believe is logical, sensible and correct, and then explicitly warn the students about the shibboleths, drumming it into them just before the exam that it's worth writing what you know the examiner wants, even though you know it's not true.

Both strategies have advantages and disadvantages. Personally I go for the second, but I can completely see why some people go for the first, and I completely respect that decision.. I just think it's very unfortunate that Edexcel forces the choice on us.

Sorry if I came over as a bit brusque in my first posting; no offence was intended, and I really hope none was taken. Now it's 3.10 a.m, and I really think I must go to sleep before I put my foot in it again.
No offence was taken at all. I'm not statistician, I don't particular like it and never studied it. This is one module I just teach with the simple aim of getting students to destroy the exam.

The general idea of the median being a 'better' average if the data is skewed is simplistic but remember this is S1.

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20. (Original post by ArcRaman)
Arsey, if i did not include the zeros in the venn diagram how many marks will i lose if any? I thought it wouldve been implied

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I doubt you will.

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