on the domain x in (-infty,infty). While statisticians and mathematicians uniformly use the term "normal distribution" for this distribution, physicists sometimes call it a Gaussian distribution and, because of its curved flaring shape, social scientists refer to it as the "bell curve." Feller (1968) uses the symbol phi(x) for P(x) in the above equation, but then switches to n(x) in Feller (1971).