Dear Attallah, your two sets of parameters are pricipally different. These parameters represent Mean and dispersion in assumption that your distribution is gaussian > 2 Mean -2.83708e-04 3.83873e-04 -3.99915e-04 3.99098e-04 > 3 Sigma 1.52598e-02 2.16818e-06 > But these parameters represent REAL Mean and dispersion of distribution seen on your histogram. Part of distribution outside of histogram is ignored. > Mean = -0.00539024 > RMS = 0.14343 > They must be the same only if distribution is GAUSSIAN and histogram contains it almost completely. But even in this case, due to different algorithms, numbers will be slightly different. Actually in your case they are pretty close. Mean is practically zero, accounting that its error is about 0.14/sqrt(1600) = 3.5E-3 RMS and Sigma also are very close. So, you see exactly what you should see. Victor -- Victor M. Perevoztchikov perev@bnl.gov perev@vxcern.cern.ch Brookhaven National Laboratory MS 510A PO Box 5000 Upton NY 11973-5000 tel office : 516-344-7894; fax 516-344-4206; home 516-345-2690
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