Gamma Distribution. The Gamma distribution (the term first used by Weatherburn, 1946) is defined as:

f(x) = (x/b)c-1 * e(-x/b) * [1/b (c)]
0 x, b > 0, c > 0

  (gamma) is the Gamma function
b     is the scale parameter
a     is the so-called shape parameter
e     is the base of the natural logarithm, sometimes called Euler's e (2.71...)

The animation above shows the gamma distribution as the shape parameter changes from 1 to 6.
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