Coal pollution mitigation emissions of sulfur dioxide or oxides of nitrogen associated with the utilization of coal in the generation of electricity." Before being adopted in this fashion, historically "clean coal" was used to refer to clean-burning coal with low levels of impurities, though this term faded after rates of domestic coal usage dropped. The term appeared in a speech to mine workers in 1918, in context indicating coal that was "free of dirt and impurities." In the early 20th century, prior to World War II, clean coal (also called "smokeless coal") generally referred to anthracite and high-grade bituminous coal, used for cooking
Count data The Poisson distribution can form the basis for some analyses of count data and in this case Poisson regression may be used. This is a special case of the class of generalized linear models which also contains specific forms of model capable of using the binomial distribution (binomial regression, logistic regression) or the negative binomial distribution where the assumptions of the Poisson model are violated, in particular when the range of count values is limited or when overdispersion is present. Count data In statistics, count data is a statistical data type, a type of data in which the observations can