The Student Room Group
Uni students - Complete our survey >>
Uni students - Complete our survey >>
Uni students - Complete our survey >>

S2 Edexcel Thursday 24th May AM - PAPER & SOLUTIONS IN FIRST POST

Scroll to see replies

Question 2b: State the probability of incorrectly rejecting H using this critical region.

Cannot believe I lost 2 marks here. Done some weird working out.
Reply 481
Avatar for Gibbo81
Gibbo81
OP
1
Original post by rfuzzy
Everyone read the mark scheme of Q5 of June 2009 S2.The question is clearly regarding poisson however they have stated below that if someone uses binomial then deduct only 1 mark!This means whichever method is correct in Q8 the other will loose only 1-2 marks!


The problem with this is that Binomial is more accurate than Poisson. So obviously if someone does Binomial instead of Poisson then they will get different, but more accurate answers. Hence only losing a mark.

In this year's question you can use Binomial easily but if you use Poisson mean is no where near variance (mean = 6 variance = 2.4 for the first part 30 and 12 for the second part) therefore the answers will be inaccurate therefore you lose all the accuracy marks and possibly some method.
Reply 482
Avatar for Jem_x
Jem_x
Original post by Scorcher
Had a shocker on this paper.

Done the wrong thing for sampling distribution, worked it out for the mean instead of the range. Completely missed the word range and assumed that it was always mean so that is 6 marks dropped. Mind went blank for the 'half a minute away from the mean' question so that's another how ever many marks dropped.

Think I dropped around 15 marks in total which is making me depressed. Especially as I think I've got 70+ in C1, C2 and S1 so far :frown: This paper could ruin me :frown:


I did the exact same thing for the sampling distribution and am hoping they will give me like one mark for listing all the possible samples :s-smilie:
Reply 483
Avatar for Gibbo81
Gibbo81
OP
1
Original post by egg123
How many marks i lose, if i work out variance by integrating with Xsquared, but then forget to stupidly take away mean squared to get correct variance, its 4 marks?


Probably 2
Original post by Gibbo81
*


1-0.9784=0.0216, not 0.0215. Am I right?
I can't believe I misread q3 a. I wrote down assumptions, not conditions. :facepalm:
Original post by Jullith
And I think I got almost every 6 or 8 mark question wrong. :cry:

Now I have to do really well in FP1 to boost my grade up. )':


are you resitting FP1? I was gutted with my result for FP1 :lol: sounds a bit stupid I got 83 its just that I got 99% in every past paper :/

for the 6 and 8 mark questions you'd get method marks fo' sure :smile:
Absolutely ecstatic about that exam, my weakest module and it looks like I'm going to achieve about 80-85 UMS... Maybe that A* in further maths might happen after all :smile:
Original post by Jem_x
I did the exact same thing for the sampling distribution and am hoping they will give me like one mark for listing all the possible samples :s-smilie:


they normally give 2 or 3 for that :wink:
Original post by Gibbo81
The problem with this is that Binomial is more accurate than Poisson. So obviously if someone does Binomial instead of Poisson then they will get different, but more accurate answers. Hence only losing a mark.

In this year's question you can use Binomial easily but if you use Poisson mean is no where near variance (mean = 6 variance = 2.4 for the first part 30 and 12 for the second part) therefore the answers will be inaccurate therefore you lose all the accuracy marks and possibly some method.


so from the 5 marker, if you did Poisson do you think you'd get 3/5 or more likely 2/5?

Also for the last question if you end up using a normal approximation because you do x~po(30) (yes facepalm) is that for certain 0/3? (Assuming you got 38 not 35 lol)
(edited 11 years ago)
Reply 490
Avatar for d3st1ny
d3st1ny
2
Original post by Gibbo81
Here are the solutions. Thanks for all the negative rep! I know Arsey is an insomniac but some of us need our beauty sleep!

It comes in two parts unfortunately (I just couldn't get it to less than 1MB).

I thought it was pretty easy with a couple of unusual questions so my best guess for grade boundaries is about 63 for an A.

Let me know what you think.

EDIT the value associated with the crit region in Q2 should be 0.0216 not 0.0215 (doing it in my head!)

People are questioning whether you should use Binomial or Poisson in the last question. Due to the values of n and p mean is not equal to variance and so a Poisson distribution will not give very accurate answers. I am sure that you will gain method marks for this question by using Poisson but the fact is that you may lose a number of accuracy marks.


You made a small mistake in Question 2:

You said P(X>=18) = 1 - 0.9784 =/= 0.0215, rather the correct ans is 0.0214

This changes the Critical region value (part b) to 0.0432 :P. [So by writing 0.0431 you will probably lose a mark xD!]
Original post by d3st1ny
You made a small mistake in Question 2:

You said P(X>=18) = 1 - 0.9784 =/= 0.0215, rather the correct ans is 0.0214

This changes the Critical region value (part b) to 0.0432 :P. [So by writing 0.0431 you will probably lose a mark xD!]


This has been pointed out 1,000 times..look at his original post he's already said it was meant to be 0.0216...besides you've just said that the correct answer was 0.0214 when it was 0.0216..so you incorrectly corrected the incorrect answer :tongue:
Original post by Gibbo81
The problem with this is that Binomial is more accurate than Poisson. So obviously if someone does Binomial instead of Poisson then they will get different, but more accurate answers. Hence only losing a mark.

In this year's question you can use Binomial easily but if you use Poisson mean is no where near variance (mean = 6 variance = 2.4 for the first part 30 and 12 for the second part) therefore the answers will be inaccurate therefore you lose all the accuracy marks and possibly some method.


Please dont destroy our hope for some pity mark . I cant believed that i got it wrong as well !! Do u think we can get 2 out of 5 ? I will be over the moon if i got that :frown:
Reply 493
Avatar for Jullith
Jullith
Original post by JordanS94
are you resitting FP1? I was gutted with my result for FP1 :lol: sounds a bit stupid I got 83 its just that I got 99% in every past paper :/

for the 6 and 8 mark questions you'd get method marks fo' sure :smile:

Nope, this is my first time doing an FP1 exam. It's my last exam, then I'm free. 8D
I felt that way about my result for D1. xD

And hopefully. :smile:
Does anyone have the answers to s1 ?
Original post by tinkerbell_xxx
Does anyone have the answers to s1 ?


http://www.thestudentroom.co.uk/showthread.php?t=2001407
hey guys i cant remeber what i put think i wrote n=35 since it was n-1. but the question before that i done the long way, P(X=0) + P(X=1) ... + P(x=8) got same answer would i lose method marks though for going long way round? and also for question 5d i intergrated for the region between 1.5<mean<2.5. thinking it was the region within the the mean is that wrong?
Original post by Gibbo81
Here are the solutions. Thanks for all the negative rep! I know Arsey is an insomniac but some of us need our beauty sleep!

It comes in two parts unfortunately (I just couldn't get it to less than 1MB).

I thought it was pretty easy with a couple of unusual questions so my best guess for grade boundaries is about 63 for an A.

Let me know what you think.

EDIT the value associated with the crit region in Q2 should be 0.0216 not 0.0215 (doing it in my head!)

People are questioning whether you should use Binomial or Poisson in the last question. Due to the values of n and p mean is not equal to variance and so a Poisson distribution will not give very accurate answers. I am sure that you will gain method marks for this question by using Poisson but the fact is that you may lose a number of accuracy marks.


Hi, was just wondering about the grade boundaries as I think I've possibly got 63 from your marksheme but i know that an A can be as high as 69-70/75, do you think that 63 would be suitable for A considering the previous papers and woul;d you say this was a reasonable paper or quite a hard paper.
Reply 498
Avatar for egg123
egg123
I got 68 , wreckon i have chance of A*?
Reply 499
Avatar for egg123
egg123
For the 2 minute, queing question, find prob of half a mintue late, I integrated pdf between 2.5 and 1.5, and this was my answer, I didnt subtract from 1, how many marks do I get for this? any suggestions?

Quick Reply

Related discussions

Latest

Trending

Trending

Articles for you