If the mean value at any node is 60 and MSE = 169 so RMSE is 13. Can I conclude that the error at my node is 60 +-13 i.e my values in this particular sample split ranges from 60-13 to 60+13. If not , what is mae/mse at each split and how do I interpret this ?
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Can I conclude that the error at my node is 60 +-13 i.e my values in this particular sample split ranges from 60-13 to 60+13.
No you cannot, because the actual error values depend on the data. For example you might have 1 instance with error 41.11 and 9 instances with error 0:
$$MSE=\frac{41.11^2+0^2+...+0^2}{10}=169$$
This example shows that the only guarantee you have for an individual absolute error is that it's lower or equal than $\sqrt{MSE \times n}$.
The MAE (mean absolute error) is easier to interpret: it's literally the mean of the absolute value of the error.
