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  1. R

    A level Statistics doubt??Post your doubts here!

    well P(X>5.2)=.9 since probability is greater then .5 we have to assume that mean is greater than 5.2 so it becomesP(Z>5.2-2sd/sd)=.9 so P(Z<5.2-2sd/sd)=.9 and then you get 5.2-2sd=1.282sd and then do the calculation for sd which is 7.24 f for 2nd part (mean-s.d<X<mean+s.d)...
  2. R

    Mathematics: Post your doubts here!

    hmm well i will give some list P(Z<a)=Φa then P(Z<-a)=1-Φa then P(Z>a)=1-Φa then P(Z>-a)=Φa then P(a<Z<b)=Φb-Φa then P(-a<Z<b)=Φb+Φa-1 then P(-a<Z<-b)=Φa-Φb hmm thats all i remmber atm
  3. R

    A level Statistics doubt??Post your doubts here!

    give me the year i will see to it
  4. R

    A level Statistics doubt??Post your doubts here!

    i i did this and got s.d as 1.58
  5. R

    Mathematics: Post your doubts here!

    and Jiyad Ahsan basically it says its within 12 from mean right? So that basically means its mean+12 and mean-12 which are 8 and 32. So P(8<X<32)=.94...P(8-20/r<Z<32-20/r)=.94....P(-12/r<Z<12/r)=.94 so if you remember that P(-a<z<b)=P(Z<b)+P(z<a)-1 apply that here so it becomes 2.P(Z<12/r)-1=.94...
  6. R

    A level Statistics doubt??Post your doubts here!

    The times taken to play Beethoven’s Sixth Symphony can be assumed to have a normal distribution with mean 41.1 minutes and standard deviation 3.4 minutes. Three occasions on which this symphony is played are chosen at random. (i) Find the probability that the symphony takes longer than 42...
  7. R

    A level Statistics doubt??Post your doubts here!

    when you dont need to use binomial distribution for the normal distribution then you dont need to do the approximation...in those case you just take 64
  8. R

    Mathematics: Post your doubts here!

    No no you got it wrong...you have to consider it to be within 12g of mean so it can 12g more/less than mean so its from 8<X<32 with prob 0.94
  9. R

    A level Statistics doubt??Post your doubts here!

    if you are talking abt the normal approximation or the continuity correction(i think) then when you calculate the mean/s.d with binomial formula(np/rootnpq) and then do normal then if its greater than say 65 you have to consider it as 65.5 if its less than 65 then its 64.5 if its greater and...
  10. R

    A level Statistics doubt??Post your doubts here!

    thanks for that in 12/61 i forgot to divide the x^2/9 thats why wasnt getting ans x.x
  11. R

    A level Statistics doubt??Post your doubts here!

    how do you find the s.d? i got the ans but i did it in a much longer way...found the sum of xsquare first and then from there on got the rest and also http://papers.xtremepapers.com/CIE/Cambridge%20International%20A%20and%20AS%20Level/Mathematics%20(9709)/9709_s12_qp_61.pdf how to get the sd in...
  12. R

    A level Statistics doubt??Post your doubts here!

    Y is 0 if same or greater minus the smaller value of x there Y can only be 0(22 44 66) 2(24 42 46 64) 4(26 62) so for 0 its (.5*.5+.4*.4+.1*.1) for 2 its (.5*.4)*2+(.1*.4)*2 and for 4 its (.5*.1)*2 Y=0 2 4 p y=.42 .48 .1(respectively) ex = .96.4=1.36
  13. R

    A level Statistics doubt??Post your doubts here!

    Well P(C) is product is even so if you list out the possibilities which are (12 14 16 21 22 23 24 25 26 32 34 36 41 42 43 44 45 46 52 54 56 61 62 63 64 65 66) so its 27/36= 3/4
  14. R

    Mathematics: Post your doubts here!

    when they ask you for approximation you are supposed to use 6.5. Also in many sums they dont ask you those and still you got to use 6.5. As far as i know if you have to get the mean/standard deviation from the binomial formula(np and Rootnpq) then you need to use 6.5 incase of less than 7. And...
  15. R

    Mathematics: Post your doubts here!

    sorry did something wrong in the first time took prob as .96 when it actually is .94 really sorry bout that basically it says its within 12 from mean right? So that basically means its mean+12 and mean-12 which are 8 and 32. So P(8<X<32)=.94...P(8-20/r<Z<32-20/r)=.94....P(-12/r<Z<12/r)=.94 so if...
  16. R

    Mathematics: Post your doubts here!

    i had to walk run and ride a three wheel driven by a human(rikshaw) for over 40mins in the rain and then entered the exam hall. half the energy was gone there oh well got s1 and a good as mark to look forward too
  17. R

    Mathematics: Post your doubts here!

    if there was time i could get some around 70 because in checking i would have figured out the vectors and another mistake but now i am looking below 60 it sucks. i mean such a long exam definitely the lengthiest from 2002-2012
  18. R

    Mathematics: Post your doubts here!

    the questions werent very hard i did really bad though but it was lengthy really lengthy and so i made silly mistakes in differential eqn and vectors 2nd part was really quite easy if i had a good read of it. i had like 10mins for both vector questions and i messed up in the 2nd one badly
  19. R

    Mathematics: Post your doubts here!

    many here also..i for one got the root3a but others got 2a and i was pretty sure i am right and they are pretty sure they are right. so unless the questions were different or many people missed something then i dont know how so many people cna be so convinced with 2 answers.
  20. R

    Mathematics: Post your doubts here!

    what was your ans to the no.5 x=2a or x=aroot3?
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