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    (Original post by Suits101)
    This is what I remember and it MAY NOT BE RIGHT

    1(a) 0,7029
    1(b) 0.669
    1(c) 0.1327
    1(d) 0.144
    1(e) 0.462 (should be 0.622?)

    2. Mean = ? s2 = ?

    3(a) 0.350
    3(b) 0.1575
    3(c) Var(x) = 2.7736
    3(d) Poisson cannot have an upper limit, people don't borrow books at a constant average rate
    3(e)(i) 30.8p
    3(e)(ii) 5.27p

    4
    (a) k = 10
    (b) P = 0.70
    (c) E(X) = 0.05
    (d) Integrate, ans = 1/300
    (e) SD(X) = 0.0289

    5(a) Test statistic = 2.3386, CV = 2.706 so accept null
    5(b) comment

    7(a) Draw graph - DENSITY function, so have to differentiate
    7(b) 61/6 but I got it wrong
    For question 6(a) the hypothesis test, I got:
    Test statistic = -2.20794
    Critical Value = -2.0537
    Reject Ho

    6(b) the confidence interval I got:
    12.61759
    20.78241



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    (Original post by 2014_GCSE)
    0.703
    0.669
    0.133
    0.144
    0.622

    mean - 31.7 o^2 - can't remember

    0.35
    0.158
    2.77
    30.8
    16.7
    10
    0.7
    0.05
    1/300
    root3 / 60
    14.9
    18.5


    ANSWER DUMP. didn't do the last 4 marker.
    Agree with all - I got what you got for 3(e)(ii) but apparently it asked for variance not SD
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    (Original post by 2014_GCSE)
    0.703
    0.669
    0.133
    0.144
    0.622

    mean - 31.7 o^2 - can't remember

    0.35
    0.158
    2.77
    30.8
    16.7
    10
    0.7
    0.05
    1/300
    root3 / 60
    14.9
    18.5


    ANSWER DUMP. didn't do the last 4 marker.
    i recognise all of these
    last one was 3.04 something, sd^2 was 2.96

    what did people get for all the wordy answers?
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    (Original post by df97)
    Hey guys! I had time at the end of the exam so I wrote down most (not all) of the answers I put on my calculator. Obviously some will likely be wrong but here's what I put so we can compare:
    1) 0.703, 0.870, 0.133, 0.144, 0.622
    2) mean=31.7 sd^2=2024.4
    3) 0.35, 0.315, 2.77, 31p, £2.77
    4) 0.7, sd(x)=0.0289
    5) Z=2.34
    6) (can't remember what I put for crit value of island A lizards), Mu(B)=15.1cm
    7) For graph I had straight horizontal line from (1, 1/4) to (4, 1/4) and then straight line going down to (6,0) and 0 otherwise.
    E(X)=3.04
    Let me know if you think any are wrong (i think 1b might be). Thanks!
    for Q3, since it's an average, you can have .8 of a penny no? If it asks for a value then then I agree round to 2sf.

    eg when you take the average amount of books, you get 3.08
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    (Original post by df97)
    For 3(b) I did 2(0.35 x 0.45) as there are two possible ways of people taking out the books (either first guy got out more than 3 and second got out less than 3 or vice versa). Not sure if I'm right but either way we have very similar answers which is good news!
    For 3(e)(ii) I did 2.77 x 10^2 as var(aX)=a^2var(X), likewise I'm unsure on this one too.
    I thought 3(e)(ii) asked for standard deviation? Damn I must've misread!

    Thanks

    (Original post by luke010203)
    For question 6(a) the hypothesis test, I got:
    Test statistic = -2.20794
    Critical Value = -2.0537
    Reject Ho

    6(b) the confidence interval I got:
    12.61759
    20.78241



    Posted from TSR Mobile
    Agree with 6(a)

    6(b) I got 16.7 +- 1.80?
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    (Original post by MahuduElec)
    About the same yes, the last Q in both had sneaky tricks
    Yeah I think the first part of the last question may have thrown people. The probability questions seemed quite long winded as well.
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    (Original post by MahuduElec)
    for Q3, since it's an average, you can have .8 of a penny no? If it asks for a value then then I agree round to 2sf.

    eg when you take the average amount of books, you get 3.08
    Exactly what I did.
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    (Original post by Suits101)
    6(b) I got 16.7 +- 1.80?
    I got this too
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    (Original post by sam_97)
    I got this too
    what was this?
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    (Original post by MahuduElec)
    for Q3, since it's an average, you can have .8 of a penny no? If it asks for a value then then I agree round to 2sf.

    eg when you take the average amount of books, you get 3.08
    I agree. I put 30.8 and then rounded it to 31p, hopefully I'll still get the mark for putting both.
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    (Original post by tanyapotter)
    what was this?
    The confidence interval in question 6, for Island B.
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    For the last question, why didn't you just put

    1/4(x-1) = 0.5

    and re-arrange for x=3?

    Therefore E(X) = 3

    I know this is wrong because it's not 4 marks worth but I don't know why it's wrong?
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    (Original post by df97)
    I agree. I put 30.8 and then rounded it to 31p, hopefully I'll still get the mark for putting both.
    You will get the mark
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    (Original post by 2014_GCSE)
    For the last question, why didn't you just put

    1/4(x-1) = 0.5

    and re-arrange for x=3?

    Therefore E(X) = 3

    I know this is wrong because it's not 4 marks worth but I don't know why it's wrong?
    0.5 is the Median value of F(x), not the mean
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    (Original post by Suits101)
    I thought 3(e)(ii) asked for standard deviation? Damn I must've misread!

    Thanks



    Agree with 6(a)

    6(b) I got 16.7 +- 1.80?
    Pretty sure your 6B is correct
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    (Original post by 2014_GCSE)
    For the last question, why didn't you just put

    1/4(x-1) = 0.5

    and re-arrange for x=3?

    Therefore E(X) = 3

    I know this is wrong because it's not 4 marks worth but I don't know why it's wrong?
    I think you might be thinking about the median there, the question was about the mean.
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    (Original post by sam_97)
    You will get the mark
    Do you know how many marks these were worth?

    1(e) - last part of Q1
    3(b) - forgot to multiply by 2, book question
    3(e)(ii) - I got 5.27p but apparently it asked for variance not SD

    Also (sorry!) what did you put about Gerald's claim? I said CI is an element of 18.7 therefore no valid/proper conclusion can be made - also what did you do for last part of 6 as I just calculated a mean and said it doesn't support belief because answer was > 18.7?
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    (Original post by 2014_GCSE)
    For the last question, why didn't you just put

    1/4(x-1) = 0.5

    and re-arrange for x=3?

    Therefore E(X) = 3

    I know this is wrong because it's not 4 marks worth but I don't know why it's wrong?
    That is the method for the median. since Fx is a cumulative function, Fx=0.5 gives the median value when solving for X
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    q1) a) 0.703 b) 0.967 (dunno if right) c) 0.133 d) 0.144 e) 0.622
    q2) I used Z so could be wrong as thinking needed to use t. mean= 31.7 var= 4.3264
    3a) 0.35 b) 0.1575 c) mean proof of 3.08, 2.7736 d) independent, possion has no top limit, random doesn't occur at a constant rate etc. e)i) 30.8 e)ii) 4.08 (i think this is what i got)
    4a) k=10 b) 0.7 c) 0.35 d) 1/300 e) (root3)/60
    5a) 2.3386 chi calc, 2.706 chi crit, hence accept H0. 5b) some logical explanation linking Observed and expected and then the suggested engine
    6a) accept H0 i think 6bi) 14.9 to 18.5 6bii) explanation 6c) mean is above 18.2 hence doesn't support his claim.
    7a) f(x) = 1/4 from x=1,2,3,4. then negative gradient from (4,1/4) to (6,0)
    7b) 73/24

    I believe most of these are right. 1b, 2, and 6bi i need conformation of these results then we'll have an unofficial mark scheme.
    grade boundaries i think will be
    A* 68-69 A 63-64 B 57-58 C 51-52
    Full UMS would be at 74/75 as easier than last year so would expect about 2 above. Hope this has helped.
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    For question 6 what were the values for the means of island A/B/C and their sample sizes? and what was the standard deviation you had to use in the confidence interval? I think it said it was unknown so had to use the t value


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