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6. Facebook reports that the average number of Facebook friends worldwide is 175.5 with a standard deviation of 90.57. If you were to take a sample of 25 students, what is the probability that the mean number Facebook friends in the sample will be 190 friends or more?

  • statistics -

    Z = (score-mean)/SEm

    SEm = SD/√n

    Find table in the back of your statistics text labeled something like "areas under normal distribution" to find the proportion/probability related to your Z score.

  • statistics -

    Solution

    My mean is 175.5
    My standard deviation is=90.57
    Sample=25

    So the probability is
    Formula to be used: P(X>190)=P((X-mean)/s
    sqrt of my sample is = 5
    (190-175.5) / 90.57/5)
    14.5 / 18.114
    calculator says 0.8004858120790548746825659710721
    I check the z-table and I see -.8 under the z of 0.00 correlates to .2119
    =0.2119

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