In hydrologic frequency analysis, a variety of
probability distribution functions, such as the gamma, lognormal,
extremevalue, and loggamma, are often examined whether they
are appropriate to the flood data or not by using some hypothesis
testing methods, because the properties of the flood data are
not well understood even now. In order to find a property of the
flood data, we can use another method: using the more general
probability distribution function which includes many types of
probability distributions used for hydrological statistics. The
4parameter extended generalized gamma distribution function is
one of such distribution functions. Two types of the extended
distributions are proposed. The parameter estimation method is
also introduced.





Extended generalized gamma distribution,
Gamma distribution, Lognormal distribution, Extremevalue
distribution,Gumbel distribution, Maximum likelihood estimation,
Homotopy method


