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Homework Help: Statistics help, Confidence interval!

  1. Jul 17, 2011 #1
    1. The problem statement, all variables and given/known data
    You look at a random sample of 64 vehicles in one school parking lot and find that 24 are trucks. Determine the 80% confidence interval for the true population proportion of trucks in all the school lots.


    2. Relevant equations
    (work shown below)


    3. The attempt at a solution

    (24) / (64) = 0.375
    σ = (.375(1-.375)) / (64)^2 = 0.605
    80% + ((1 – 8%) / 2) = 90% = 0.9
    z=1.28 ~ 0.9
    Margin of error = 1.28 * 0.0605 = 0.07744
    LL= .375 - .07744 = .29756
    UL= .375 + .07744= .45244
    (.29756, .45244)
     
  2. jcsd
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