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Any non-linear differentiable function, (,), of two variables, and , can be expanded as + +. If we take the variance on both sides and use the formula [11] for the variance of a linear combination of variables (+) = + + (,), then we obtain | | + | | +, where is the standard deviation of the function , is the standard deviation of , is the standard deviation of and = is the ...
In contrast to the mean absolute percentage error, SMAPE has both a lower and an upper bound. Indeed, the formula above provides a result between 0% and 200%. Indeed, the formula above provides a result between 0% and 200%.
In some disciplines, the RMSD is used to compare differences between two things that may vary, neither of which is accepted as the "standard". For example, when measuring the average difference between two time series , and ,, the formula becomes
Relative uncertainty is the measurement uncertainty relative to the magnitude of a particular single choice for the value for the measured quantity, when this choice is nonzero. This particular single choice is usually called the measured value, which may be optimal in some well-defined sense (e.g., a mean, median, or mode). Thus, the relative ...
For example, we might want to calculate the relative change of −10 to −6. The above formula gives (−6) − (−10) / −10 = 4 / −10 = −0.4, indicating a decrease, yet in fact the reading increased. Measures of relative change are unitless numbers expressed as a fraction. Corresponding values of percent change would be ...
To illustrate, a simple example of this process is to find the mean and variance of the derived quantity z = x 2 where the measured quantity x is Normally distributed with mean μ and variance σ 2. The derived quantity z will have some new PDF, that can (sometimes) be found using the rules of probability calculus. [ 7 ]
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Consider the previous example with men's heights and suppose we have a random sample of n people. The sample mean could serve as a good estimator of the population mean. Then we have: The difference between the height of each man in the sample and the unobservable population mean is a statistical error, whereas; The difference between the ...