Description:
About 1998 Oregon solid waste
The Department of Environmental Quality (DEQ) for the State of Oregon has compiled data on the amount of solid waste generated, recovered and disposed for each of the 34 counties in Oregon (plus the Portland metropolitan area or Metro). Counties and Metro are referred to as "wastesheds" by the DEQ, a term analagous to watershed in hydrology; a wasteshed collects solid waste into a concentrated waste stream. Solid waste monitored by the DEQ includes both household waste (garbage, recyclables, etc.) and some industrial waste such as construction debris, but apparently does not include industrial wastes from manufacturing, agricultural processing, petrochemical plants, etc.
Data are given on the population and tons of solid waste disposed in 35 wastesheds in Oregon in 1998. Disposal takes place by both landfilling and incineration. Though not stated, operators of these two types of disposal facilities presumably monitor the disposed tonnage and report these values to the DEQ.
The amount of solid waste disposed each year depends upon the amount generated or produced and the amount recycled or recovered. The production rate is probably strongly correlated with population, whereas the recycling rate depends upon a large number of factors, including the proportion of recyclables in the waste stream, ease of recycling, education programs, etc.
Population size is most likely the dominant variable in waste disposal, and the graph supports this assumption, showing a strong positive correlation between population and solid waste disposed in 1998. The relationship between people and waste disposed is linear, with a very high correlation coefficient. The slope of the regression line gives a typical "disposal rate" of a bit less than 1 ton of solid waste per citizen per year. Note that the Y-intercept is not zero; what is the significance, if any, of a non-zero intercept?
The datum for the Portland metropolitan area has been excluded from the graph, to better view the majority of data points. Is the Metro datum an "outlier"? Students could run regressions both excluding and including this datum; how different are these regressions?
