Hey there! Sign in to join this conversationNew here? Join for free
x Turn on thread page Beta

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

    2
    ReputationRep:
    (Original post by Bloom77)
    Yep
    The last question was particularly difficult
    Not sure why the grade boundaries were quite high


    Posted from TSR Mobile
    It was 58 for an which is isn't too bad, if I came out of the exam I would cry.
    Yh I couldn't get the last part of question 7.
    Offline

    16
    ReputationRep:
    (Original post by Bloom77)
    How do you know the area of a triangle is 0.5 in this question?
    For part C

    Attachment 556817

    Mark scheme
    Attachment 556819


    Posted from TSR Mobile
    As the mean = mode we know that it is symmetrical (i.e. the area is shared between the two halves of the f(x))
    Offline

    2
    ReputationRep:
    (Original post by Billsonbubbles)
    No you don't but dont worry about it,


    I think you need to work out the probabilities, but you do need to convert to Z values and look in the normal distribution table ?

    If thats what you were asking.

    But make sure you add a continuity correction in there , as you are approximating a discrete to a continuos random variable..

    Enjoy and hope that helped

    Will
    Thanks

    Also regarding normal approximation for a hypothesis test, say your testing whether there's a decrease (for example X=20). With your continuity correction you would do P(X<20.5) right? So if testing for an increase you would do P(x>19.5)?

    What would you do if your just testing for a change in the value of X?

    Thanks again
    Offline

    2
    ReputationRep:
    https://57a324a1a586c5508d2813730734...%20Edexcel.pdf

    Question 1? how do i do it
    Offline

    2
    ReputationRep:
    Dont worry fixed my problem
    Offline

    2
    ReputationRep:
    Its a continuous uniform distribution
    Offline

    2
    ReputationRep:
    (Original post by keres)
    Its a continuous uniform distribution
    yeah but i dont get why the mark scheme got -0.5 and 0.5
    Offline

    2
    ReputationRep:
    (Original post by imran_)
    yeah but i dont get why the mark scheme got -0.5 and 0.5
    If something was measured to the nearest cm then error is 0.5 cm each way

    E.g.
    I measured my height to be 155.4 cm. This is 155cm to the nearest cm. But if I was 154.7 cm this would also be 155 cm to nearest cm.

    In fact, if I was any height between 154.5 cm to 155.5 cm then I would be 155cm to the nearest centimetre.

    this is gcse upper and lower bounds x
    Offline

    1
    ReputationRep:
    (Original post by imran_)
    yeah but i dont get why the mark scheme got -0.5 and 0.5
    +or- half scale division? thats what i would have thought.
    Offline

    8
    ReputationRep:
    https://57a324a1a586c5508d2813730734...%20Edexcel.pdf

    guys how do you approach q3c.

    I'm kind of confused about how you start it

    https://57a324a1a586c5508d2813730734...%20Edexcel.pdf

    PLEASE SOMEONE REPLY
    Offline

    21
    ReputationRep:
    (Original post by iMacJack)
    As the mean = mode we know that it is symmetrical (i.e. the area is shared between the two halves of the f(x))
    Thank you!


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

    21
    ReputationRep:
    Very Important Poster
    A distribution X is used to model the length, in mm, of the first tear of a uPhone charger, and the PDF is specified below. However, Wapple have been careless and have lost some key details of the PDF.

    kx(1-x) if  0 \leq x &lt; 0.5

    \frac{23}{40} - \frac{3x}{20} if    0.5 \leq x \leq b

    0 otherwise.

    a) Given that b is the minimum value greater than 0 such that f(b) = 0, find the value of b.

    b) Hence find the value of k.

    c) Find the expected length of the tear and the standard deviation.

    d) Wapple send out an inspector to 5 random people who had asked for refunds. If the tear is longer than 1mm for at least 3 customers, all five will be refunded (ignoring systematic/human error). Find the probability, to 2 s.f, of Wapple giving a refund to a random group of 5 customers who have complained.

    Spoiler:
    Show


    (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.

    Offline

    16
    ReputationRep:
    (Original post by SeanFM)
    A distribution X is used to model the length, in mm, of the first tear of a uPhone charger, and the PDF is specified below. However, Wapple has been careless and have lost some key details of the PDF.

    kx(1-x)    if 0 \leq x &lt; 0.5
    \frac{23}{40} - \frac{3x}{20}    if   0.5 \leq x \leq b



0 otherwise.

    a) Given that b is the minimum value greater than 0 such that f(b) = 0, find the value of b.

    b) Hence find the value of k.

    c) Find the expected length of the tear and the standard deviation.

    d) Find the interquartile range of the length of tears.

    e) Wapple send out an inspector to 5 random people who had asked for refunds. If the tear is longer than 1mm for at least 3 customers, all five will be refunded (ignoring systematic/human error). Find the probability, to 2 s.f, of Wapple giving a refund to a random group of 5 customers who have complained.
    I will do this question, however could you fix the latex pls?
    • Very Important Poster
    • Thread Starter
    Offline

    21
    ReputationRep:
    Very Important Poster
    (Original post by iMacJack)
    I will do this question, however could you fix the latex pls?
    Working on that as we speak. Shouldn't be too hard to read though.
    Offline

    16
    ReputationRep:
    Marking June 14 (r) and then I'll get onto that question SeanFM
    Offline

    16
    ReputationRep:
    70/75 in June 14 (r)

    Ok - now to Sean's q...
    Offline

    2
    ReputationRep:
    https://57a324a1a586c5508d2813730734...%20Edexcel.pdf

    how would I do question 4? idk where to start from

    SeanFM
    • Very Important Poster
    • Thread Starter
    Offline

    21
    ReputationRep:
    Very Important Poster
    (Original post by imran_)
    https://57a324a1a586c5508d2813730734...%20Edexcel.pdf

    how would I do question 4? idk where to start from

    SeanFM
    It's to do with the critical region, the % significance and what value of k is most suitable (see from tables, trial and error)
    Offline

    16
    ReputationRep:
    (Original post by SeanFM)
    A distribution X is used to model the length, in mm, of the first tear of a uPhone charger, and the PDF is specified below. However, Wapple have been careless and have lost some key details of the PDF.

    kx(1-x) if  0 \leq x &lt; 0.5

    \frac{23}{40} - \frac{3x}{20} if    0.5 \leq x \leq b

    0 otherwise.

    a) Given that b is the minimum value greater than 0 such that f(b) = 0, find the value of b.

    b) Hence find the value of k.

    c) Find the expected length of the tear and the standard deviation.

    d) Find the interquartile range of the length of tears.

    e) Wapple send out an inspector to 5 random people who had asked for refunds. If the tear is longer than 1mm for at least 3 customers, all five will be refunded (ignoring systematic/human error). Find the probability, to 2 s.f, of Wapple giving a refund to a random group of 5 customers who have complained.
    Is part a B = 23/6? I have a feeling I have done something wrong
    Offline

    0
    ReputationRep:
    Name:  q3b.png
Views: 77
Size:  67.9 KB Anybody know how to do 3b? It's from the june 2013 paper, I looked at exam solution but I still don't understand why you start off with p(x>n), how do we know that we should use it this way around?
 
 
 
Reply
Submit reply
Turn on thread page Beta
Updated: August 20, 2016
Poll
Do you agree with the proposed ban on plastic straws and cotton buds?

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.