Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

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
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Can you offer guidance or do you also need help?