John Gordon Skellam (1914-1979) was a

statistician A statistician is a person who works with theoretical or applied statistics. The profession exists in both the private and public sectors. It is common to combine statistical knowledge with expertise in other subjects, and statisticians may wor ...

and

ecologist Ecology () is the study of the relationships between living organisms, including humans, and their physical environment. Ecology considers organisms at the individual, population, community, ecosystem, and biosphere level. Ecology overlaps wi ...

, who discovered the

Skellam distribution The Skellam distribution is the discrete probability distribution of the difference N_1-N_2 of two statistically independent random variables N_1 and N_2, each Poisson distribution, Poisson-distributed with respective expected values \mu_1 and \mu ...

. Skellam was born in

Staffordshire Staffordshire (; postal abbreviation Staffs.) is a landlocked county in the West Midlands region of England. It borders Cheshire to the northwest, Derbyshire and Leicestershire to the east, Warwickshire to the southeast, the West Midlands Cou ...

. He was educated at Hanley High School where he won several scholarships including free admission to New College in Oxford. He was one of the most respected members of the British Region of the

Biometric Society The International Biometric Society (IBS) is an international professional and academic society promoting the development and application of statistical and mathematical theory and methods in the biosciences, including biostatistics. It sponsors th ...

. In 1951, John G. Skellam developed the reaction-diffusion model of

invasion biology An invasive species otherwise known as an alien is an introduced species, introduced organism that becomes overpopulated and harms its new environment. Although most introduced species are neutral or beneficial with respect to other species, i ...

. This model describes the dynamics of populations, which simultaneously develops and spreads, and provides that the invasion front moves with constant speed. He explained on the basis of habitation

muskrat The muskrat (''Ondatra zibethicus'') is a medium-sized semiaquatic rodent native to North America and an introduced species in parts of Europe, Asia, and South America. The muskrat is found in wetlands over a wide range of climates and habitat ...

introduced to

Europe Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a Continent#Subcontinents, subcontinent of Eurasia ...

that only by chance the species may be in a place where it would have to grow. Skellam has provided a model that allows to take the dynamics of populations as a

random variable A random variable (also called random quantity, aleatory variable, or stochastic variable) is a mathematical formalization of a quantity or object which depends on random events. It is a mapping or a function from possible outcomes (e.g., the po ...

at any time t. Its stochastic form is much more flexible than previous deterministic equations.

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1914 births 20th-century British zoologists English statisticians Alumni of New College, Oxford 1979 deaths 20th-century English mathematicians People from Hanley, Staffordshire {{UK-statistician-stub

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