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Thread: Hypothesis testing with no stated standard deviation

  1. #1

    Hypothesis testing with no stated standard deviation




    My head is going to explode, can someone help before it is too late?

    Te problem:

    According to the government, 23% of all American adults have more than one job. A random survey of 68 adults finds that 21 of them hold more than one job. At the 5% level of significance, can we accept the government's claim?

    Let me see, I have the (sorry don't know how to write formula on here)
    H0: mu = .23 which is the stated average by the government.
    H1: mu not = .23
    alpha = 0.05
    n= 68
    x bar= .309 (percentage of sample 21/68 = .309)

    I am at a loss here. Maybe I am stupid, but I don't see enough info to get a standard deviation and complete the problem. Am I missing something? Someobody help me please.

    By the way... there are a few more problems I will post seperately because I am dying here.

  2. #2
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    For this one you would test:

    Ho: P = 0.23
    Ha: P <> 0.23

    The sample p ("small" p) = 21/68 = 0.309

    The standard error of proportions is SEp = sqrt(PQ/n) where

    P = .23
    Q = 1-.23 = .77
    n = 68

    Z = (p - P)/SEp

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