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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).
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.
where a t is the actual value of the quantity being forecast, and f t is the forecast. MAD is the mean absolute deviation. The formula for the MAD is: = | | where n is the number of periods. Plugging this in, the entire formula for tracking signal is:
where is the actual value of the quantity being forecast, is the forecast, and is the number of different times for which the variable is forecast. Because actual rather than absolute values of the forecast errors are used in the formula, positive and negative forecast errors can offset each other; as a result, the formula can be used as a ...
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Michael Fish - A few hours before the Great Storm of 1987 broke, on 15 October 1987, he said during a forecast: "Earlier on today, apparently, a woman rang the BBC and said she heard there was a hurricane on the way.
A "persistence" forecast can still rival even those of the most sophisticated models. An example is: "What is the weather going to be like today? Same as it was yesterday." This could be considered analogous to a "control" experiment. Another example would be a climatological forecast: "What is the weather going to be like today? The same as it ...
Robin John Hyndman (born 2 May 1967 [citation needed]) is an Australian statistician known for his work on forecasting and time series. He is a Professor of Statistics at Monash University [1] and was Editor-in-Chief of the International Journal of Forecasting from 2005–2018. [2]