Random number generation from right-skewed, symmetric, and left-skewed distributions

Monte Carlo simulations have become a mainstream technique for environmenta l and technical risk assessments. Because their results are dependent on th e quality of the involved input distributions, it is important to identify distributions that are flexible enough to model all relevant data yet effic ient enough to allow thousands of evaluations necessary in a typical simula tion analysis. It has been shown in recent years that the S-distribution pr ovides accurate representations for frequency data that are symmetric or sk ewed to either side. This flexibility makes the S-distribution an ideal can didate for Monte Carlo analyses. To use the distribution effectively, metho ds must be available for drawing S-distributed random numbers. Such a metho d is proposed here. It is shown that S-distributed random numbers can be ef ficiently generated from a simple algebraic formula whose coefficients are tabulated. The method is shown step by step and illustrated with a detailed example. (The tables are accessible in electronic form in the FTP parent d irectory at http://www.musc.edu/similar to voiteo/ftp/.).