1. A study compared floral diversity between croplands and wetlands. Independent random samples of 120 cropland regions and 61 wetland regions were obtained in the Southern Great Plains. The cropland regions contained an average of 15.03 native floral species, with a standard deviation of 4.83; the wetland regions had an average of 16.76 and a standard deviation of 4.95.

(a) Test if the mean number of native floral species is lower in cropland regions. Use the 1% significance level.

(b) Obtain a two-sided 99% confidence interval for the difference in mean number of floral species between cropland and wetland regions.

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The Air Quality Index (AQI) is used to measure air quality near roadways and industrial regions in large cities. Governments report AQI values for common pollutants to keep the public informed about air quality. AQI values of 0-50 are regarded as good, 51-100 as moderate, 101-150 as unhealthy for sensitive individuals, 151-200 as unhealthy, 201-300 as very unhealthy, and beyond 300 as hazardous.

The following table gives AQI values for S02 (Sulphur Dioxide) and CO (Carbon Monoxide) from a random sample of 20 locations in California, between the years 2000 and 2010.