Blurb::
Aleatory uncertain variable - gamma

Description::
The gamma distribution is sometimes used to model time to complete a task, such as a repair or service task. It is a very flexible distribution with its shape governed by alpha and beta.

The density function for the gamma distribution is given by: 
\f[ f(x) = \frac{ {x}^{\alpha-1} \exp \left( \frac{-x}{\beta} \right) }
                { \beta^{\alpha}\Gamma(\alpha) },
\f]
\f$\mu = \alpha\beta,\f$ and \f$\sigma^2 = \alpha\beta^2\f$. 
Note that the exponential distribution is a special
case of this distribution for parameter \f$\alpha = 1\f$.

Topics::	continuous_variables, aleatory_uncertain_variables
Examples::

Theory::
When used with some methods such as design of experiments and
multidimensional parameter studies, distribution bounds are inferred
to be [0, \f$\mu + 3 \sigma\f$].

For some methods, including vector and centered parameter studies, an
initial point is needed for the uncertain variables. When not given
explicitly, these variables are initialized to their means.

Faq::
See_Also::	
