Math Is Fun Forum
  Discussion about math, puzzles, games and fun.   Useful symbols: √ ∞ ≠ ≤ ≥ ≈ ⇒ ∈ Δ θ ∴ ∑ ∫ π -




Not registered yet?

  • Index
  •  » Help Me !
  •  » [Discrete Math] Finals review problems in Probability

Post a reply

Go back

Write your message and submit
:) :| :( :D :o ;) :/ :P :lol: :mad: :rolleyes: :cool: | :dizzy :eek :kiss :roflol :rolleyes :shame :down :up :touched :sleep :wave :swear :tongue :what :faint :dunno

Go back

Topic review (newest first)

2013-06-15 22:17:52

I have not once seen a question asking for proof by contradiction, or counter-example. I don't even think it's mentioned in any of the textbooks! There is a Further Maths module called FP1 which uses proof by induction, and some 'standard' proofs needed for arithmetic and geometric series in C1 and C2, but other than that, I have honestly never seen those...

Do you know if that was an outlier (the candidate getting a D in a module)? I remember us having a discussion before that the examiners were very flexible -- but that incident you recalled makes me feel as though one could have a nasty examiner who feels like punishing a few students...

I really hate the re-mark system. It's unreasonable for them to charge upwards of 40 just for one paper, I think -- and having wasted money on this in the past, you never get any kind of feedback, just a piece of paper saying what the remarked score was. Many students, particularly at my school, can't afford it.

For universities, I've heard that Cambridge look at your STEP scripts if you were very close to meeting the grade, and make some sort of subjective judgement based on your perceived ability... but other than that, I would be interested in hearing if people have been successful in circumstances like these. I do know that if a candidate has an offer of A*AA, and ends up achieving AAA, they might still be accepted if they had some other candidates who also didn't achieve A*AA -- H (from the FP1 thread) even got into her AAB uni despite getting ABC in her A-levels!

I'm going to uni next September, yes -- currently still in Year 13, enjoying being a kid just for a little while longer!
I doubt there is any expertise that I could pass on...

bob bundy
2013-06-15 20:32:45

zetfunc wrote:

Wasn't the trig question a proof question? That's normally how they assess that one.

I'd argue that is stretching the meaning of 'proof' somewhat.  The spec. talks about 'methods', contradiction and counter example.  The trig isn't even an identity.  But it's the nearest I'm going to get I suppose.  I'll have a look at some past papers, when I get a moment.

If a candidate comes out with A*, A*, A*, A*, and A* on five modules and then C on this one, I think the chief examiner would be looking very carefully at that candidate's answers.  At least, I'd hope that would happen.

Many years ago (before the A* grade existed) I had a computer studies student who got A, A,  A,  A,  A, and D, on his modules.  I asked for a photocopy of his paper  and the marker (red ink in those days) had marked him down on every answer.  If my student hadn't used the exact wording on the mark scheme, two marks became one or zero.  I was ready to appeal the grade.  But by this time, he was at the university of choice doing a computing course, so he said don't bother. 

There are a number of options for appeal; increasingly costly, depending on what you want.  Back then, you could pay for a photocopy of the paper; ask for a clerical re-check (not much use as they just check they've added up the marks correctly); or a full re-mark.  If the re-mark comes out with a better grade, they re-fund the cost.  There are deadlines for submitting and it's not much help if you're trying to get to a Uni and the re-mark takes until November.

If one of your friends just misses the grades, my advice would be to contact the university admissions directly and ask them to take the mix up into consideration.  Might work.  But, I cannot see it coming to that. 

Btw, I've lost track of where you are in the process.  All those early entries has confused me.  dizzy  Am I right that you are not at uni yet?  Do let us know your final pathway once you get all your results and offers sorted.  Then maybe you should consider becoming a full member of MIF so you can pass on your expertise.  smile


2013-06-15 18:49:53

I agree -- I personally think that people are just jumping on the scapegoat bandwagon. There were always tough papers in the past (especially M4/M5 last year!) yet no one complained, and there were some paper leaks last year too.

The tricky bit I think is the 2nd solution to the last part of the functions question. I didn't spot that at first. The contextual question (Q8) seemed standard, but the extra information was strange, not something I've seen too often in an Edexcel maths paper...

That's definitely the right spec -- but supposedly they are making changes to it next year, with the scrapping of January exams from now on...

Wasn't the trig question a proof question? That's normally how they assess that one.

I just don't understand how there are people claiming to have got A*s in all their C3 mocks yet lost 40 marks on this paper, it seriously doesn't make any sense. I think the steam is just exacerbated by the fact that they leaked the papers again...

bob bundy
2013-06-15 17:53:13

hi zetafunc,

Thanks for the link; I've edited into an url.

I cannot see what all the fuss is about.  That paper looks pretty straight forward to me.  Q8. ? As they lead you through what to do, I don't even think the context is confusing.  Exam boards get pressured from outside to try to make questions 'real life' and this is probably their attempt.  hhhmmmm smile didn't work, did it?

I'm looking at … 180510.pdf

As far as I can tell that is the correct specification.  The questions all conform to that.  The only issue I have is with a bit on page 31

Edexcel wrote:

Methods of proof, including proof by contradiction and disproof by
counter-example, are required. At least one question on the paper
will require the use of proof.

I cannot see where they have done this on the paper.  I would not regard algebraic manipulation as a 'proof'.

If I were checking this paper, prior to use, I would criticise it for that reason.  But I wouldn't think candidates are disadvantaged because Edexcel forgot to have proof on the paper.  It's not possible to set a paper that has absolutely everything in it.  Odd that they set themselves this requirement.  I'd have written 'Questions requiring the use of proof may be set.' 

Or am I looking at an out-of-date spec.?  It says new in 2009, which, in exam board terms, could mean it has been re-written twice by now. smile
But, it's the one that comes up when you search their site. ???


2013-06-15 04:56:12

The link is here: … ?t=2381111

Having looked at the paper just now, I don't really understand what the fuss is about... it seems mostly pretty standard with the exception of a couple of marks (the context of the question in Q8 seems completely pointless). Then again, I sat C3 2 years ago so I am not sure if my opinion is accurate...

Whilst I agree that it is only one module, a number of my friends are quite distressed given that they need an A* in maths (which is dependent mainly on only C3 and C4 in which an average of 90 is needed). I am just curious about how they are dealing with the 60 candidates who sat the original (leaked) paper -- how can they reliably discredit a student who genuinely achieved full marks? Wouldn't the papers need separate grade boundaries?

Supposedly, M2, M3, FP1, C3, C4, FP2 and FP3 were all leaked -- although they have no direct evidence that people are in possession of the papers (they just seem to know that a batch of them went missing in a van or something).

bob bundy
2013-06-15 04:25:12

hi zetafunc

This was news to me.  (too busy digging the garden smile )

Edexcel has said this … ement.aspx

If they'd just set a hard paper (without all the bother about leaks)  students would probably have had a moan and got on with life.  But there seems to be a 'head of steam' building over this.  I think you and your friends should relax about it and get on with the rest of the exams as best you can.

(i) it is only one module (you don't fail in all exams because of one module);

(ii) they have said they'll adjust the marks using the usual UMS system, and I believe them;

(iii) they're bound to look very, very carefully at this for C3 this year, because they know the world is watching and is ready to jump on them if there is the slightest suspicion that they've been unfair.  If anything, I'd guess they'll be more generous than usual but, of course, they won't admit that openly.  smile

I'd like to see a copy of the paper so I can make my own judgement about the questions.  Maybe it is too soon for it to become public; couldn't find a download; if you know of one please post a link.


2013-06-15 01:23:46

bob bundy wrote:


Hi bob,

I was wondering what you thought of the recent paper leak (for the second year running!) from Edexcel, resulting in complaints from over 10,000 students who sat the C3 paper yesterday? My friends are quite distressed about the situation...

2013-06-14 23:17:55

What a fine looking person!

2013-06-14 23:16:08

Turned my image downside-up to make it easier to compare my resemblance with Bob's. Pretty close, I reckon, and probably from the same ancestral stock.

Looks like the lefty/righty combination complement each other; just waiting now for the avalanche of compliments on our appearance. We made a special effort for this. smile

2013-06-14 11:03:40

Hi Bob,

Funny you had your sketch done downside-up! Were you hanging from a tree branch at the time? And have you got a massive arm span, and can hang from a branch by your toes?

At least I went to the barber and the dentist and got rid of that unbecoming piece of jewellery before my sketch!

I do see a faint resemblance between us, though: 2 eyes, 2 ears, a nose and a mouth...and you appear to be a lefty.

2013-06-14 04:57:40

Same here. We have more in common than it seems.

bob bundy
2013-06-14 03:26:46


Phro wrote:

You'll have to do a screen print and compare with Bob's after he's done his, and maybe you can find some similarity between you two

For Stefy's sake I hope he doesn't look a bit like this.  Omg, but how did they know about the earring and bunches?



2013-06-14 01:21:01

I really don't know. You're the only one I've ever come across to hold that title (self-proclaimed or otherwise), and I didn't question its validity when you used it to sign off that post a while back. There may be other (pretend or genuine) GNs, of course, but I'd only be guessing.

Whichever. I take it that you didn't grammar-check the presentation prior to its release, then. Pity...the blunder has now been picked up and blurted out to the world. I would have suggested to them a good GN, if I'd known in time. smile

2013-06-14 00:51:08

phrontister wrote:

the Grammar Nazi

Aren't there many Grammar Nazis, not just one?

2013-06-14 00:35:42

Trying to reach the younger (text-typing) and older generations in one fell swoop, I guess. Or maybe it wasn't grammar-checked by the Grammar Nazi prior to publication. smile

Board footer

Powered by FluxBB