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  2. Numeric precision in Microsoft Excel - Wikipedia

    en.wikipedia.org/wiki/Numeric_precision_in...

    Excel maintains 15 figures in its numbers, but they are not always accurate; mathematically, the bottom line should be the same as the top line, in 'fp-math' the step '1 + 1/9000' leads to a rounding up as the first bit of the 14 bit tail '10111000110010' of the mantissa falling off the table when adding 1 is a '1', this up-rounding is not undone when subtracting the 1 again, since there is no ...

  3. Symmetric mean absolute percentage error - Wikipedia

    en.wikipedia.org/wiki/Symmetric_mean_absolute...

    The earliest reference to a similar formula appears to be Armstrong (1985, p. 348), where it is called "adjusted MAPE" and is defined without the absolute values in the denominator. It was later discussed, modified, and re-proposed by Flores (1986).

  4. Mean absolute percentage error - Wikipedia

    en.wikipedia.org/wiki/Mean_absolute_percentage_error

    This little-known but serious issue can be overcome by using an accuracy measure based on the logarithm of the accuracy ratio (the ratio of the predicted to actual value), given by ⁡ (). This approach leads to superior statistical properties and also leads to predictions which can be interpreted in terms of the geometric mean.

  5. Round-off error - Wikipedia

    en.wikipedia.org/wiki/Round-off_error

    In the IEEE standard the base is binary, i.e. =, and normalization is used.The IEEE standard stores the sign, exponent, and significand in separate fields of a floating point word, each of which has a fixed width (number of bits).

  6. Observational error - Wikipedia

    en.wikipedia.org/wiki/Observational_error

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  8. Mean absolute error - Wikipedia

    en.wikipedia.org/wiki/Mean_absolute_error

    Quantity disagreement is the absolute value of the mean error: [4] | = |. Allocation disagreement is MAE minus quantity disagreement. It is also possible to identify the types of difference by looking at an ( x , y ) {\displaystyle (x,y)} plot.

  9. Tracking error - Wikipedia

    en.wikipedia.org/wiki/Tracking_error

    Under the assumption of normality of returns, an active risk of x per cent would mean that approximately 2/3 of the portfolio's active returns (one standard deviation from the mean) can be expected to fall between +x and -x per cent of the mean excess return and about 95% of the portfolio's active returns (two standard deviations from the mean) can be expected to fall between +2x and -2x per ...