Ian Chen 發問時間: 科學數學 · 8 年前

我有統計學問題~急><

I have two questions below:

1. in a group of 200 college students, 138 are enrolled in a course in psychology, 115 are enrolled in a course in sociology, and 91 are enrolled in both. how many of these students are not enrolled in either course?

2. four candidates are seeking a vacancy on a school board.if a is twice as likely to be elected as b, and b and c are given about the same chance of being elected, while c is twice as likely to be elected as d, what are the probabilities that 1) c will win? 2) a will not win?

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  • 8 年前
    最佳解答

    1 N(psychology) = 138, N(sociology) = 115

    N(psychology and sociology) = 91

    N(psychology or sociology)

    = 138 + 115 - 91

    = 162

    N(not enrolled in either course)

    = 200 - 162

    = 38

    2(1) Let the winning probability of d is x, then b and c is 2x, a is 4x

    As there should be one of a, b,c or d to be elected

    x + 2x + 2x + 4x = 1

    x = 1/9

    So, P(c will win) = 2/9

    2(2) P(A will not win) = 1 - 4x = 5/9

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