SOLUTION: Testing the variance
Suppose an airline claims that its flights are consistently
on time with an average delay of at most 15 minutes. It claims that the average delay is so co
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Suppose an airline claims that its flights are consistently
on time with an average delay of at most 15 minutes. It claims that the average delay is so co
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Question 1058050: Testing the variance
Suppose an airline claims that its flights are consistently
on time with an average delay of at most 15 minutes. It claims that the average delay is so consistent that the variance is no
more than 150 minutes. Doubting the consistency part of the claim, a disgruntled traveler calculates the delays for his next
25 flights. The average delay for those 25 flights is 22 minutes with a standard deviation of 15 minutes.
My questions below
what is the df=_______ ?
Let a= 0.05
Decision ________
Conclusion write out in complete sentence Answer by rothauserc(4718) (Show Source):
You can put this solution on YOUR website! Our Ho is variance = 150 minutes and H1 is variance > 150 minutes
:
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degrees of freedom(df) = sample size - 1 = 25 - 1 = 24
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Note that variance = (standard deviation)^2
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variance of the sample = 15^2 = 225
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H1 does not contain an =, therefore we use a one-tailed test
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Our test statistic is calculated
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c = ((25 - 1) * 225) / 150 = 36
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alpha(a) = 0.05
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we check the chi-square distribution table
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df of 24 and a = 0.05 gives us a probability value(p-value) of 0.0549
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since our p-value > 0.05, there is no reason to reject our null hypothesis(Ho)
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