# a measure for MAE (of a regression)

I'm running a grid search, in order to fine-tune a NN hyper parameters. the question is: the MAE values I get from the trainings are too close. since I have the statistical attributes of the target values, is there a way to somehow come up with a starting value for MAE, where the worst regression can achieve.

I think the question is not clear. the value I'm looking for, is analogous to a probability for classification problems. (example: an neural network which is supposed to classify the inputs into 8 possible classes, will have accuracy of 0.125 just by random classification of inputs. so a 12.5% accuracy is the measure for such classifier) now, I have the Mean, and StdDev (and other stats if need be) of the target values of my samples. how can I calculate a measure to judge my MAE (and not by comparing different MAE values from different trainings)?

• yes, MAE:mean absolute error. I'm tryna come up with a value for MAE, that even a non trained NN can achieve. (like the worst MAE. I know it's worst possible value is +inf. but wht I'm looking for is a value like E where I can validly say: "my NN should have MAE values of less than E. because even a untrained NN can achieve a MAE of E or less.") Commented May 9, 2019 at 7:42
• I tried to explain the thing I'm looking for, by exemplifying the classification analogue. (an 8-class NN classifier, should do better than %12.5 accuracy. cuz any damn classifier can achive that 12.5 accuracy just by randomly choosing a class. (of course, assuming the class probability distribution is uniform)) Commented May 9, 2019 at 7:45
• In a classification problem, the baseline scenario is not to emit randomly, but to emit default class distributions. For example if the distribution of classes in training data is 70% class A and 30% class B, then you output these figures not 50/50. In the regression case the baseline scenario is the mean only model for Squared Error, or median only model for Absolute Error. For this reason the most basic model always emits the median of the training values (median of the targets, not inputs), and you can calculate MAE from this value. Commented May 9, 2019 at 8:50
• THANK YOU. exactly it is. median for MAE. I suggest this should better be posted as answer than a comment, as it is the exact answer for the question. I calculated the median of targets array and MAE (assuming all predictions are median value) and it gives a values close to MAE of my untrained NN. so this is correct. Commented May 9, 2019 at 8:58