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The mean of nonresidential buildings is 30 years and the standard deviation of the ages of the buildings is 5 years. Determine the probability that a random sample of a group of 50 nonresidential buildings will have a mean age of less than 27.5 years.

  • 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 the Z score.

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