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Math Help - A total of 4 buses carrying 148 student

  1. #1
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    A total of 4 buses carrying 148 student

    Question : A total of 4 buses carrying 148 student from the same school arrive at a football stadium. The buses carry 40, 33, 25 and 50 students. One of the students is randomly selected. Let X denote the number of students that were on the bus carrying this randomly selected student. One of the 4 bus drivers is also randomly selected. Let Y denote the number of students on his bus.
    i) Which of E[X] or E[Y] do you think is larger? Why ?
    ii) Compute E[X] and E[Y]

    ---------------------------------------My Work-----------------------
    Bus A --------Pr(Student from A) = \frac{40}{148}

    Bus B --------Pr(Student from B) = \frac{33}{148}

    Bus C --------Pr(Student from A) = \frac{25}{148}

    Bus D --------Pr(Student from A) = \frac{50}{148}

    X would be the number of student from the bus chosen

    but i dont know what to do ???
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  2. #2
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    Well, you've sussed out the distribution of students so thats a good start. Perhaps the easier start would be to list what your random variables are and their respective probabilities:

    X P(X)
    25 25/148
    33 33/148
    40 25/148
    50 50/148

    Y P(Y)
    25 1/4
    33 1/4
    40 1/4
    50 1/4

    Do you see why?

    From here it is elementary to answer parts i and ii.
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  3. #3
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    Here i am getting

    E[X] = 39.29

    E[Y] = 37...................Are these correct????
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  4. #4
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    Yes.
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  5. #5
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    thanks mite
    wish u a happy and prosporous new year
    cheers
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