George S. Fishman
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Achieving specific accuracy in simulation output analysis
This paper extends the use of the regenerative property of queueing systems in the analysis of simulation output. In particular, it describes a sequential estimation method which when used with the regenerative property allows results to be obtained with specified statistical accuracy. This method includes a test to check the normality assumption on which the sequential procedure relies. The paper illustrates the method using the empty and idle state as the regenerative state. A second example then describes how using the most frequently entered state as the regenerative state reduces the chance of making a costly error in a preliminary simulation run. The paper also described how a variance reduction method due to Page [9] can be used to obtain a specified accuracy with considerably fewer job completions than are required when no variance reduction technique is applied.
Sampling from the gamma distribution on a computer
This paper describes a method of generating gamma variates that appears to be less costly than Wallace's recently suggested method. For large shape parameter &agr;; the cost of computation is proportional to √&agr;, whereas Wallace's method is proportional to &agr;. Experimentation by Robinson and Lewis indicates that for small &agr; the method suggested here also dominates methods recently suggested by Dieter and Ahrens, albeit those methods dominate for large &agr;. The method suggested here uses the rejection technique.
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