Determination of parameters of the three-parameter Weibull distribution by a graphic-calculation method

A graphic-calculation method for determining parameters of the three-parameter Weibull distribution is described. The a position parameter is determined by following the form of the Henry's curve on the Weibull probability paper. The given value of the parameter a for which the Henry's curve passes into the Henry's straight line, represents the point evaluation of the a position parameter. After the determination of the a position parameter the three - parameter Weibull distribution is transformed into the two-parameter one of which the b proportion parameter and the c form parameter are determined by the method of the Henry's straight line on the Weibull probability paper. In order to illustrate the application of this method, the article gives on example of determining the parameters a, b and c by a computer and the given calculating program.