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Population mean help, Statistics!

  1. Jul 17, 2011 #1
    1. The problem statement, all variables and given/known data
    Assume that the population is normal with some unknown mean and standard deviation of 25. A sample size 400 is taken. The resultant sample mean is 67.
    a.) What is your best estimate for the value of the population mean?
    b.) What is the value of the standard error?
    c.) In the 99% confidence interval for the sample mean, what is teh value the margin of error?
    d.) Construct the 99% confidence interval for the population mean (give Lower Limit and Upper Limit).

    2. Relevant equations
    (work shown below)

    3. The attempt at a solution
    a.) 67
    b.) 25/(400)^1/2 = 25/20 = 5/4
    c.) 2.58 * (5/4) = 3.225
    d.) LL= 67-3.225 = 63.775
    UL= 67+3.225 = 70.225
    (63.775, 70.225)
  2. jcsd
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