Question

A researcher knows from past studies that the standard deviation of the time it takes to...

  1. 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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