Question

With a previous contractor, the mean time to replace a streetlight was 3.2 days. A city councilwoman thinks that the new contractor is not getting the streetlights replaced as quickly. She selects a random sample of 12 streetlight service calls and obtains the following times to replacement (in days).
(a) Because the sample size is small, she must verify that replacement time is normally distributed and the sample does not contain any outliers. The normal probability plot
and boxplot are shown. Are the conditions for testing the hypothesis satisfied?
(b) Is there enough evidence to support the councilwoman’s belief at the α = 0.05 level of significance?


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  • CreatedApril 28, 2015
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