Gumbel+ (Upper) Distribution
The Gumbel+ (Upper) distribution is an extreme maximum value distribution. It is also known as a Type I upper extreme value distribution.
Calculations
The probability density function, f(t), and the survival function, that is reliability, 
, with respect to time t, follows for computing Gumbel+ (Upper) distributions.
, with respect to time t, follows for computing Gumbel+ (Upper) distributions.
Where:
In this case, δ and ξ are the scale and location parameters of the distribution. If a location parameter is used, see Location Parameter for additional calculation information.