33. Growth and air pollution. Government officials have difficulty attracting new business to communities with troubled reputations. Nevada has been one of the fastest growing states in the country for a number of years.

Accompanying the rapid growth are massive new construction projects. Since Nevada has a dry climate, the construction creates visible dust pollution. High pollution levels may paint a less than attractive picture of the area, and can also result in fines levied by the federal government.

As required by government regulation, researchers continually monitor pollution levels. In the most recent test of pollution levels, 121 air samples were collected.

The dust particulate levels must be reported to the federal regulatory agencies. In the report sent to the federal agency, it was noted that the mean particulate level 57.6 micrograms/

cubic liter of air, and the 95% confidence interval estimate is

(52.06 mg to 63.07 mg). A graph of the distribution of the particulate amounts was also included and is shown below.

a) Discuss the assumptions and conditions for using Student’s t inference methods with these data.

b) Do you think the confidence interval noted in the report is valid? Briefly explain why or why not.

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20 Lhu 0 0 20 40 60 80 100 Particulates (in micrograms per cubic liter of air)