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Edexcel S2 - 27th June 2016 AM Watch

  • View Poll Results: How did you find the Edexcel S2 exam?
    Very hard
    145
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    331
    33.57%
    Normal
    293
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    Easy
    152
    15.42%
    Very easy
    65
    6.59%

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    (Original post by AJC1997)
    grade boundary predictions? I got somewhere between 62-70 and need 80UMS in this exam
    it will drop down this year - I would say 62 maybe even 60 for an A as this was SO much harder than the 2015 paper
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    (Original post by fefssdf)
    thats exactly what I did !
    The expected value of A = the expected value of Pi * R^2.

    So it's Pi * E(R^2) rather than Pi times (E(R))^2.
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    (Original post by iipebblesii)
    I got this too
    Essentially A is not modelled by a continuous uniform distribution so you can't use it. Instead you need to use the formula in the formula book
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    (Original post by iipebblesii)
    I got this too
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    HOW TO FIND E(A)

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    (Original post by hwilkoo)
    Can someone please explain E(A), as i got it to equal 49pi.

    E(R) = (9+5)/2
    E(R) = 7

    E(A) = pi * 7^2
    E(A) = 49pi
    A = pi*R^2
    E(A) = E(pi*R^2)
    E(A) = pi*E(R^2)

    so you had to work out Var(R) ( I think it was 4/3 or something?), and E(R) (7), and then use Var(R) = E(R^2) - E(R)^2, so E(R^2) = Var(R) + E(R)^2 = 4/3 + 49 = 151/3. So E(A) = piE(R^2) = 151pi/3 = 158.1.
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    (Original post by fefssdf)
    it will drop down this year - I would say 62 maybe even 60 for an A as this was SO much harder than the 2015 paper
    No way, this was easier than most simple because there were 2 long 'prove that' questions so people will get those. It'll be standard boundaries at the least


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    (Original post by Mattematics)
    The expected value of A = the expected value of Pi * R^2.

    So it's Pi * E(R^2) rather than Pi times (E(R))^2.
    Thought that could be the case! Thanks
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    (Original post by Supermanxxxxxx)
    For the 8 marker I got n=87 but I think I messed up when hiding the quadratic how many marks do you think Tisi Weill be


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    i messed this up as well - I got like n=62 lol - you should get like 5/8 if you got up to making a quadratic tbh
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    That was horrible!
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    (Original post by iMacJack)
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    HOW TO FIND E(A)

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    i did it by integration but fair enough
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    (Original post by M3WIZARD)
    Question 1a) U = 1.44 Var(x) = 1.44 (3 Marks)b) U was approximately Variance (1 Mark)c) I – 0.251 II – 0.777 (4 Marks)d) 0.1378 (3 Marks)e) 0.152 (3 Marks) (Might be 0.132 – Rushed this onmy copy of answers) Question 2a) N=60 (2 Marks)b) I – 0.0133 II -0.0159 (5 Marks)c) 0.2396>0.01 Keep H0 (5 Marks)Question 3a) f(x) = ¼ 5=<R=<9 , 0 otherwise (1 Marks)b) 0.5 (1 Marks)c) 158.13 (4 Marks)Question 4a) Show that (6 Marks)b) K = 1/9 (4 Marks)Question 5 N = 225(I applied continuity correction – I honestly didn’t know if I should) (8Marks)Question 6a) 9 samples (2 Marks)b) 4 = ¼ , 5 = 3/10 , 6= 29/100 , 7 = 3/25, 8 =1/25 (5 Marks)c) N=57 (3 Marks)Question 7a) 1.2 (4 Marks)b) 0.24 (4 Marks)c) 0.325 (3 Marks)d) £41.88 (2 Marks)e) Shouldn’t remove staples (2 Marks) I’m not claiming these are all right – let me know J These are what I wrote
    Got the same except the mean for the first one was 1.41.


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    (Original post by Nikhilm)
    No way, this was easier than most simple because there were 2 long 'prove that' questions so people will get those. It'll be standard boundaries at the least


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    really... well are you suggesting it will be higher than 67 for an A cause that seems very unlikely...
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    Went alright but was nothing like the past papers. Got stuck on finding k for 20 minutes and decided to move on, how did you guys do it? I got k = 1/(a+21) and couldnt hew another equation in a from it
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    (Original post by hwilkoo)
    Can someone please explain E(A), as i got it to equal 49pi.

    E(R) = (9+5)/2
    E(R) = 7

    E(A) = pi * 7^2
    E(A) = 49pi
    Same here..?
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    (Original post by iMacJack)
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    HOW TO FIND E(A)

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    (Original post by ThatPerson2)
    A = pi*R^2
    E(A) = E(pi*R^2)
    E(A) = pi*E(R^2)

    so you had to work out Var(R) ( I think it was 4/3 or something?), and E(R) (7), and then use Var(R) = E(R^2) - E(R)^2, so E(R^2) = Var(R) + E(R)^2 = 4/3 + 49 = 151/3. So E(A) = piE(R^2) = 151pi/3 = 158.1.

    Thanks guys, i get it now
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    (Original post by exclamationmark)
    How many marks was it to find the sample distribution of the other means?
    I think 5 marks
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    I thought it was an ok paper and I didn't revise anything until half an hour before the exam and I'd like to think I got a safe B but I feel screwed for D2 tomorrow
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    (Original post by fefssdf)
    really... well are you suggesting it will be higher than 67 for an A cause that seems very unlikely...
    I sat S2 last year as well (got 69/75) and i'd have to say the grade boundaries would be about 67 for an A
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    How did I find this harder than fp2
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    [5,9]
    I did 5^2pi = 25pi and 9^2pi = 81pi
    Then i wrote [25pi,81pi]
    E(X) = 1/2(25pi+81pi)
    = 53pi
 
 
 
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