Hey there! Sign in to join this conversationNew here? Join for free

Edexcel S2 - 27th June 2016 AM watch

  • View Poll Results: How did you find the Edexcel S2 exam?
    Very hard
    145
    14.71%
    Hard
    331
    33.57%
    Normal
    293
    29.72%
    Easy
    152
    15.42%
    Very easy
    65
    6.59%

    Offline

    3
    ReputationRep:
    Please could someone explain question 4f https://57a324a1a586c5508d2813730734...%20Edexcel.pdf thank you
    Offline

    12
    ReputationRep:
    (Original post by veldt127)
    Edexcel D2 is on Wednesday :'(
    Oh snap I feel sorry for you I thought I was unlucky with S2!
    Offline

    5
    ReputationRep:
    (Original post by SeanFM)
    a. b = 23/6

    b. k = 2

    c E(X) = 1.39. E(X^2) = 2.70. Var(X) = 0.77. Deviation = 0.88 (answers within that range, depending on rounding etc)

    d. IQR question removed - takes too much time.

    e. 0.69.






    Well done the last bit should be 2 s.f but doesn't matter really. Just something to be wary of in the exam if they specify how many s.f you need.
    What have I done wrong for part e?

    Probability of the tear being longer than 1mm for one customer is o.575

    Probability of tear being longer than 1mm for 3 or more customers is binomial with n = 5, p = 0.575
    Then P(X>=3) = P(x=3) + P(x=4) + P(x=5)?

    I got 0.64
    Offline

    2
    ReputationRep:
    (Original post by AlphaArgonian)
    Oh snap I feel sorry for you I thought I was unlucky with S2!
    I'm not too stressed thanks to doing well in AS papers, but I also have Physics on Tuesday which is going to be hell
    Offline

    2
    ReputationRep:
    Hey. Can I have some help with this question? (January 2002)
    Name:  jan2002.png
Views: 50
Size:  33.2 KB

    The question says "more than 196 passengers turn up" so its >196. Then, wouldn't it mean that (less than or equal to) 4 do not turn up?

    The mark scheme says simply < 4, so I am confused.
    Offline

    3
    ReputationRep:
    (Original post by SeanFM)
    Afraid not - k is a whole number - actually, let me double check that. I think I've messed it up :lol:

    Yes - k should be a whole number. Phew.
    k = 2, but surely for your last question, it's 1-0.69 not 0.69?

    EDIT: damn nah you're right lol nvm
    Offline

    2
    ReputationRep:
    (Original post by SeanFM)
    Should be closest. Please post a link to the paper



    Correct. The binomial distribution (a discrete one) takes no values between 6 and 6.9, so those two things are equivalent.
    So it's not <=7, as 6.9 is closer to 7 than to 6?
    Offline

    12
    ReputationRep:
    (Original post by veldt127)
    I'm not too stressed thanks to doing well in AS papers, but I also have Physics on Tuesday which is going to be hell
    Fair enough, good luck!
    Offline

    5
    ReputationRep:
    (Original post by Aliceeee12)
    Hello Everyone,

    Hope revision is well

    Please could somebody help me in the June 2014 R paper question 5c
    https://57a324a1a586c5508d2813730734...%20Edexcel.pdf

    How come they poisson to normal approximate rather than binomial to normal approximate because isnt binomial more accurate?
    You don't know what the probability of a defect occuring is so you can't use binomial. You're told the rate but the mean is 25 so you need to approximate to normal.
    Offline

    16
    ReputationRep:
    (Original post by ktbunny)
    thank you so much!
    i just realised i need someone to explain the answer to another question, could you help me again?

    Attachment 556965
    2b)

    the answer is 1 Because it is continuous and much like a normal distribution the probability of a single number is 0 therefore the probability that it does equal that number is 0 so then 1-0 = 1.
    Offline

    3
    ReputationRep:
    (Original post by apzoe)
    Hey. Can I have some help with this question? (January 2002)
    Name:  jan2002.png
Views: 50
Size:  33.2 KB

    The question says "more than 196 passengers turn up" so its >196. Then, wouldn't it mean that (less than or equal to) 4 do not turn up?

    The mark scheme says simply < 4, so I am confused.
    Because you're binomial for part (a) should be number who do NOT show up, so it is less than 4
    Offline

    2
    ReputationRep:
    John picks 10 real numbers randomly from 12 to 17. Find the probability that at least 5 of thesenumbers are greater than 15.5.
    Offline

    3
    ReputationRep:
    Do we need to know the proofs of E(X) and Var(X) for binomial or just the proofs of these for uniform distribution?
    Offline

    20
    ReputationRep:
    Question:
    6aii

    I don't understand why we are looking at the upper critical value and not the lower critical value as it says minimum

    Attachment 556929

    MS: Attachment 556931








    Posted from TSR Mobile
    • Very Important Poster
    • Thread Starter
    Offline

    21
    ReputationRep:
    Very Important Poster
    (Original post by apzoe)
    So it's not <=7, as 6.9 is closer to 7 than to 6?
    No, you don't round. round or anything like that here. In a discrete distribution, you can only have x =0, 1, 2, 3, 4, 5, 6, 7,... etc.

    So if I said X=< 6.9, then it is true that X =< 6. It is not true that X =< 7, because if X were 7 then X would not be =< 6.9. So you round down when the inequalities are that way round.

    Converse is when X >= 7.1 - you can infer that X >= 8.
    Offline

    2
    ReputationRep:
    (Original post by Mattematics)
    You don't know what the probability of a defect occuring is so you can't use binomial. You're told the rate but the mean is 25 so you need to approximate to normal.
    Thankyou loadssss
    Offline

    1
    ReputationRep:
    Hey there, does anyone have a good resources for learning the thousands of definitions that there are in S2?
    thanks
    Offline

    2
    ReputationRep:
    (Original post by Nikhilm)
    Because you're binomial for part (a) should be number who do NOT show up, so it is less than 4
    I mean that the mark scheme says less than 4, while I was thinking it should be less than or equal to 4.

    So that P(X>196) = P(Y<=4) (not = P(Y<4))
    • Very Important Poster
    • Thread Starter
    Offline

    21
    ReputationRep:
    Very Important Poster
    (Original post by Mattematics)
    What have I done wrong for part e?

    Probability of the tear being longer than 1mm for one customer is o.575

    Probability of tear being longer than 1mm for 3 or more customers is binomial with n = 5, p = 0.575
    Then P(X>=3) = P(x=3) + P(x=4) + P(x=5)?

    I got 0.64
    Yeah.. your working is right.

    But probability of being longer than 1mm I make to be 0.602.
    • Community Assistant
    Offline

    18
    ReputationRep:
    Community Assistant
    (Original post by SSD07)
    is it because you don't know which side is the shorter side??? so it could be either which is why you add the probabilities for both??
    The perimeter is 20cm, so the sum of the two sides is half the perimeter, which is 10cm. so x+y =10, consider the end points x=1; when x=1 x+y=10, so y=9.

    When X=7, y=3, so it adds up to 10. so 1<x<7 and 3<y<9

    Now either x or y can be the longer side, depending on their length. You're looking for the longer side to be more than 6cm, so that's when x>6 and y>6. When is y>6 when x<... (remember x+y=10). Then add the probabilities.

    --------------------------
    Or think about it like this 1<X<7, so 3<Y<9,

    X~U[1,7] and Y~U[3,9], then work out the probabilities of both being greater than 6.
 
 
 
Poll
Do you agree with the PM's proposal to cut tuition fees for some courses?

The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

Write a reply...
Reply
Hide
Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.