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Homework Help: How do you find a critical value when using a 1% significance level

  1. Aug 29, 2008 #1
    1. The problem statement, all variables and given/known data

    The data i'm working with is
    Sample mean(voltage)=128.25
    variance=9/20
    sample size=20
    SD=3
    Z=-2.61



    3. The attempt at a solution

    The first part of what I was doing was a hypothesis test that the true voltage is 130 compared to the alternative less than 130. Which I worked out the Z= -2.61

    What I have to do now is calculate the critical value for this test using a 1% significance level.. I know the answer because I looked it up in the text book its 128.44 but for the life of me I can't work out any formulas that will help me... can anyone shed some light??? Thanks :)
     
  2. jcsd
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