Thursday, February 23, 2006

Acronyms - in Hebrew???

There are a multitude of performance measures in statistics and data mining. These tend to have acronyms such as MAPE and RMSE. It turns out that even after spelling them out, it is not always obvious to users how they are computed.

Inspired by Don Brown's The Da Vinchi Code, I devised a deciphering method that allows simple computation of these measures. The trick is to read from right-to-left (like Hebrew or Arabic). Here are two examples:

RMSE = Root Mean Squared Error
1. Error: compute the errors (actual value - predicted value)
2. Squared: take a square of each error
3. Mean: take an average of all the squared errors
4. Root: take a square root of the above mean

MAPE = Mean Absolute Percentage Error
1. Error = compute the errors (actual value - predicted value)
2. Percentage = turn each error into a percentage by dividing by the actual value and multiplying by 100%
3. Absolute = take an absolute value of the percentage errors
4. Mean = take an average of the absolute values
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