• Q: If the mean of the following frequency distribution is 39.35 , find the value of f1.

    C.I   4-14 14-24 24-34 34-44 44-54 54-64 64-74
    f   6 9 f1 9 9 7 8

    where:-
    C.I → class interval, f → frequency, C.M → class mark Share to Whatsapp



  • Given that data:

    C.I   f   C.M(x)    f*x
    4-14  6 9  54
    14-24  9 19  171
    24-34  f1 29  29 f1
    34-44  9 39  351
    44-54  9 49  441
    54-64  7 59  413
    64-74  8 69  552
    ∑f= 48+f1 ∑f*x= 1982+29 f1

    ie. Mean = (∑f*x)/(∑f)

  • ie. Mean = (∑f*x)/(∑f)
    =>39.35 = (1982 + 29 f1) /(48 + f1)
    =>39.35 * (48 + f1) = (1982 + 29 f1)
    =>(39.35 * 48) + (39.35 * f1) = 1982 + 29 f1
    =>(1888.8) + (39.35 * f1) = 1982 + 29 f1
    =>[(39.35) - 29]f1 = 1982 - (1888.8)
    =>[10.35]f1 = 93.2
    =>f1 = 93.2/10.35
    =>f1 = 9.0048309178744
    ie. f1 = 9

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