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Math Help - check my working

  1. #1
    Junior Member
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    Jun 2010
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    check my working

    Dear

    please find the attached file of questions.

    please check my working .
    i will be very thankful to you.



    Ans 2 b)
    there are 5C3 (because order does not matter)ways of having a group of 3 from this finite population. So there are 10 groups and you have to find the mean of each of the 10 groups.
    6 6 9->7
    6 6 15->9
    6 6 18->10
    6 9 15->10
    6 9 15->10
    6 15 18->13
    6 15 18->13
    6 9 18->11
    6 9 18->11
    9 15 18->14
    Then it is asking you to find the average of the averages that you have found.
    (7+9+10+10+10+13+13+11+11+14)/10=10.8

    The variance is
    [(7-10.8)2+(9-10.8)2+(10-10.8)2+(10-10.8)2+(10-10.8)2+ (13-10.8)2+(13-10.8)2+(11-10.8)2+(11-10.8)2+(14-10.8)2]/(10-1)=4.4


    Ans 3 c)
    estimator with min. standard error that is variance of T is better estimator.
    variance of T1=V(X1+X2+ X3 /3)
    = V( X1 /3) +V(X2/3) + V(X3 /3)

    = 1/9 V(X1) + 1/9 V(X2)+ 1/9V(X3) = 1/3 σ2
    SIMILARLY FIND v(T2)
    v(T2)=3/8σ2
    as variance of T1 is less,it is better estimator


    Ans 1 .b)
    If all 5 are selected without replacement, there is only one way in which all 5 have tomatoes, C(5,5) = 1. Total number of ways of selecting 5 cans from 10 = C(10,5) = 180
    Hence, required probability of selecting all tomatoes = 1/180 ≈ 0. 005556

    [IMG]file:///C:/DOCUME%7E1/KHYBER%7E1/LOCALS%7E1/Temp/msohtml1/01/clip_image001.gif[/IMG]
    The total number of ways of selecting 3 or more tomatoes is:
    C(5,3)*C(5,2) + C(5,4)*C(5,1) + C(5,5) = 126

    Total number of ways of selecting 5 cans from 10 = C(10,5) = 180
    Hence, required probability of selecting 3 or more tomatoes = 126/180 = 0.7


    Attached Thumbnails Attached Thumbnails check my working-qno3-part-3.gif   check my working-qno02-part-3.gif   check my working-qno01-part-2.gif  
    Last edited by CaptainBlack; July 10th 2010 at 12:07 AM.
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  2. #2
    Grand Panjandrum
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    It would help if you typed the questions with your solutions. It is a lot of trouble to switch between the browser and image file viewer windows.

    In would also help if each of the questions and solutions were in seperate thresds.

    CB
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