Question
A researcher knows from past studies that the standard deviation of the time it takes to...
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A researcher knows from past studies that the standard deviation of the time it takes to inspect a car is 18 minutes. A random sample of 28 cars is selected and inspected. The standard deviation for this sample is 22.5 minutes. At alpha=.05, can it be concluded that standard deviation for this sample is greater than 18 minutes?
Homework Answers
Answer #1
Given : Sample size=n=28
Sample standard deviation=s=22.5
Hypothesized value=
Significance level=
Hypothesis : 
VS 
The critical value is ,
; The Excel function is ,=CHIINV(0.05,27)
The value of the test statistic is ,
Decision : Here , the value of the test statistic is lies in the rejection region.
Therefore , reject Ho.
Conclusion ; Hence , there is sufficient evidence to support the claim that standard deviation for this sample is greater than 18 minutes.
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