The Environmental Protection Agency releases figures on urban air soot in selected cities in the United States. For the city of St. Louis, the EPA claims that the average number of micrograms of suspended particles per cubic meter of air is 82. Suppose St. Louis officials have been working with businesses, commuters, and industries to reduce this figure. These city officials hire an environmental company to take random measures of air soot over a period of several weeks. The resulting data follow. Assume that the population standard deviation is 9.184. Use these data to determine whether the urban air soot in St. Louis is significantly lower than it was when the EPA conducted its measurements.

Let α = .01. If the null hypothesis is rejected, discuss the substantivehypothesis.

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