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Monte Carlo Analysis<br />

Introduction to Uncertainty Analysis<br />

This is, in some sense, the best estimate possible of the expectation. The sample variance, which<br />

estimates the variance of the probability distribution of Y, is given by:<br />

This estimate of the variance and its square root (called the experimental standard deviation)<br />

characterizes the variability of the observed values Y i , or their dispersion about their mean.<br />

Figure 11-1. Central Tendency and Dispersion<br />

A Monte Carlo experiment (with 1,000 runs, for example) provides one single realization of the<br />

random variables (sample mean, variance, and so on). However, this realization is not useful if<br />

the result does not come with a reliable confidence interval. Figure 11-1 shows an interval<br />

that encloses the mean . This interval characterizes the precision obtained by<br />

the Monte Carlo estimator of the mean.<br />

In practice, the coefficient of variation and the relative standard error of mean<br />

are often used to quantify the relative variability (or obtained precision) of one<br />

given estimator . The Eldo Monte Carlo flow uses the following definition of the RSEM if the<br />

mean is non-zero:<br />

412<br />

Eldo® User's Manual, 15.3

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