ABSTRACT
Data on air pollution in 41 U.S. cities were collected by Sokal and Rohlf (1981) from several U.S. government publications and are reproduced here in Table 3.1. (The data are also given in Hand et al., 1994.) There is a single dependent variable, so2, the annual mean concentration of sulphur dioxide, in micrograms per cubic meter. These data are means for the three years 1969 to 1971 for each city. The values of six explanatory variables, two of which concern human ecology and four climate, are also recorded; details are as follows:
temp: average annual temperature in ◦F manuf: number of manufacturing enterprises employing 20 or
more workers pop: population size (1970 census) in thousands wind: average annual wind speed in miles per hour precip: average annual precipitation in inches days: average number of days with precipitation per year The main question of interest about these data is how the pollution
level as measured by sulphur dioxide concentration is determined by the six explanatory variables. The central method of analysis will be multiple regression.
