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      Random
      Sample
                                                                       Statistics
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             Chi-square (χ2) Distribution
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                        t Distribution
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                       F Distribution
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   •As n gets large the bias goes to zero
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                                                                Null
      Alternative                                             Hypothesis
      Hypothesis
        •In this example, H1 is a two-sided alternative hypothesis
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•H1 in equation 3-22 is a two-sided alternative hypothesis
•The procedure for testing this hypothesis is to:
   − take a random sample of n observations on the random variable x,
   − compute the test statistic, and
   − reject H0 if |Z0| > Zα/2, where Zα/2 is the upper α/2 percentage of the
     standard normal distribution.
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 One-Sided Alternative Hypotheses
• In some situations we may wish to reject H0
  only if the true mean is larger than µ0
    – Thus, the one-sided alternative hypothesis is H1:
      µ>µ0, and we would reject H0: µ=µ0 only if Z0>Zα
• If rejection is desired only when µ<µ0
    – Then the alternative hypothesis is H1: µ<µ0, and
      we reject H0 only if Z0<−Zα
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               Confidence Intervals
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 Confidence Interval on Mean, Variance Known
    Furthermore, a 100(1 − α)% upper confidence bound on µ is
    whereas a 100(1 − α)% lower confidence bound on µ is
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• For the two-sided alternative hypothesis, reject H0 if |t0| > tα/2,n-1, where
 tα/2,n-1, is the upper α/2 percentage of the t distribution with n − 1 degrees of
 freedom
• For the one-sided alternative hypotheses,
      • If H1: µ1 > µ0, reject H0 if t0 > tα,n − 1, and
      • If H1: µ1 < µ0, reject H0 if t0 < −tα,n − 1
• One could also compute the P-value for a t-test
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   • Section 3-3.4 describes hypothesis testing and confidence intervals
    on the variance of a normal distribution
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   • Section 3-4.3 describes hypothesis testing and confidence intervals
    on the variance of two normal distributions
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