ABSTRACT
The next set of data to be considered in this chapter concerns air pollution in 41 cities in the United States. Observation for the first five cities are shown in Table 10.2. Air pollution is measured by sulphur dioxide concentration and recorded as a binary variable indicating whether the annual mean concentration of sulphur dioxide (over the years 1969-1971) is below 30 mg=m3 or above or equal to this value. The values of six explanatory variables are also recorded, two of which relate to human ecology and four to climate. In detail the variables are as follows:
Hiso2: 0¼ SO2< 30 mg=m2 1¼ SO2 30 mg=m2
Temperature: Average annual temperature in 8F Factories: Number of manufacturing enterprises employing 20 or more
workers Population: Population size in thousands Wind speed: Average wind speed in miles per hour Rain: Average annual precipitation in inches Rainy days: Average number of days with precipitation each year.
