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Age at onset of dementia was determined for a sample of adults between the ages of 60 and 75. For 15 subjects, the results were ÓX = 1008, and Ó(X-M)2 = 140.4. Use this information to answer the following:

  • statistics -

    mean = 1008/15 = 67.2
    sd =sqrt(140.4/14) = 3.167

    z = (x1 - 67.2)/3.167

    x1 = 1*3.167 + 67.2 = 70.37

    z = (x2 - 67.2)/3.167
    -1 = (x2 - 67.2)/3.167
    x2 = -1*3.167 + 67.2 = 64.033

    The ages are 60 and 70 respectively.

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