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The Official Edexcel S2 Jan 2010 Thread watch

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    No they asked for the probabiltity x<0 which is px<=-1 so the answer is 1/6

    F(0) = P(X<=0) they asked for p(x<0)...so F(0) would not work
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    (Original post by James Greenham)
    No they asked for the probabiltity x<0 which is px<=-1 so the answer is 1/6
    This method is correct when dealing with discrete distributions ie P(X<0) = P(X<=-1)

    However the question is dealing with a continuous distribution where it can be said P(X<0) = P(X<=0)
    this is due to the fact that P(X=0) = 0.

    hope this helps.
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    (Original post by ben_1991)
    This method is correct when dealing with discrete distributions ie P(X<0) = P(X<=-1)

    However the question is dealing with a continuous distribution where it can be said P(X<0) = P(X<=0)
    this is due to the fact that P(X=0) = 0.

    hope this helps.

    Ben is correct in this case, if you have been taught S2 from the new Heinemann books, it isn't clearly stated that when P(X<0) = P(X<=0) for continuous distribution and P(X<0) = P(X<=-1) ONLY for discrete distributions.
    If you have access to the old Heinemann series (blue book) it is more explicitly stated.

    I got critical Region 2 and 17
    Did the Mean probabilities wrong for the last question
    and Robot question I did conditional but got over 1 so flipped the fraction (for no apparent reason), (well actually so I would get less than one) ...

    what marks am i bound to get anyone?:confused: x
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    (Original post by ben_1991)
    ill add my 2 cents to the questions people seem to be also disagreeing on!

    (2a) P(X<0) = 1/3

    (3d) same as part (3b) due to independence

    (4b) F(x)=
    0 for x<0
    1/27(x^3-3x^2+6x) for 0<x<=3
    1/3(x-1) for 3<x<=4
    1 for x>4

    (6b+6c) critical regions X<=2 X>=16 sig level 0.85%
    all your answers are correct.
    i got the independance thing wrong as i said 3d=3c by mistake

    whats the definition for critical regoin by the way???
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    (Original post by kosy91)
    whats the definition for critical regoin by the way???
    i put:
    the critical region is the range of value where if the test statistics lies, would lead to the rejection of the null hypothesis, H0.
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    (Original post by ben_1991)
    i put:
    the critical region is the range of value where if the test statistics lies, would lead to the rejection of the null hypothesis, H0.
    i said critical region contains critical values that lead to rejection of null hypothesis(H0)
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    so how did everyone find it? im not too sure
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    (Original post by Moa)
    Edexcel S2 - Tuesday 19 January 2010 Paper: (warning, very poor quality)
    Spoiler:
    Show








    noooooooooooooooo...

    I got as a Critical region C<=1 and C=>11

    pleas tell me that is not c<=2 and C=>16 !!!!!!!!!!!!

    NOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO OOOO
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    has any1 posted the unofficial markscheme of jan 2010 yet?? pls let me know :|
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    i doubt thay have
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    (Original post by James Greenham)
    No they asked for the probabiltity x<0 which is px<=-1 so the answer is 1/6

    F(0) = P(X<=0) they asked for p(x<0)...so F(0) would not work
    no its continuous distribution so you dont change the P(X<0) to P(X<=-1)
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    (Original post by [email protected]@y)
    noooooooooooooooo...

    I got as a Critical region C<=1 and C=>11

    pleas tell me that is not c<=2 and C=>16 !!!!!!!!!!!!

    NOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO OOOO
    sory but i found the second one
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    Has anyone got a good copy of the paper and some solutions yet?
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    for question three did people use binomial or poisson??
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    (Original post by viki_91)
    for question three did people use binomial or poisson??
    poisson
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    (Original post by john1234567)
    poisson
    garr i knew it everyone used poisson i dont even know why i used binomal because i know its wrong. do u think i will lose all ten marks?
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    (Original post by viki_91)
    garr i knew it everyone used poisson i dont even know why i used binomal because i know its wrong. do u think i will lose all ten marks?
    i suppose if you used the right principles you might get a few method marks
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    (Original post by viki_91)
    garr i knew it everyone used poisson i dont even know why i used binomal because i know its wrong. do u think i will lose all ten marks?
    my freind did that too.

    but the word 'rate' at the start of the question gave the hint that it was poisson
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    i knew i got the critical region wrong.. lol.. i got the actualy significance as 0.. haha.. yeh probs looked at wrong bit of table! gosh.. lol.. hmmm..
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    i have lost 5 marks. not more hopefully.
    how much do you guys think my final UMS will be? can i expect anything over 90? or will it be 86-88-ish??
 
 
 
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