Count models are a subset of discrete response regression models. Count data are distributed as non-negative integers, are intrinsically heteroskedastic, right skewed, and have a variance that increases with the mean. Example count data include such situations as length of hospital stay, the number of a certain species of fish per defined area in the ocean, the number of lights displayed by fireflies over specified time periods, or the classic case of the number of deaths among Prussian soldiers resulting from being kicked by a horse during the Crimean War.