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Just a quick question: I am building an ML model right now, however, I am receiving very similar (72.2 and 72.4 for example)% for both Accuracy and F1-Score on my Validation Dataset and my unseen Test Dataset, respectively. This is occurring on most of the baseline models I have produced for my problem right now.

Is this showing that my model is completely overfitting or just acting completely random and getting lucky?

Thanks

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  • $\begingroup$ To check if your model is overfitting you will have to compare against the performance on the training set. Do you find performance metrics on the train set significantly higher than the out of sample test sets? $\endgroup$ Commented May 6, 2021 at 15:58
  • $\begingroup$ Performance is extremely similar which is worrying me? $\endgroup$ Commented May 6, 2021 at 19:52
  • $\begingroup$ Ok, try training the model on a much smaller train set. Check if that increases performance on train set and degrades performance on test set. $\endgroup$ Commented May 7, 2021 at 4:01
  • $\begingroup$ @JayaramIyer The OP said the magic word unseen Test Set - so your comment does not hold. He's doing the right thing $\endgroup$ Commented Feb 25, 2023 at 20:03

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If the training set, validation set and the unseen test set (as you put it) have the same score, but lower than you expected then the model has not overfitted.

An overfitted model would have higher scores for the training data at least, and depending on how you optimised the hyper parameters on the validation data but lower for the unseen test set.

The more likely outcome is that your model has underfitted i.e. low but consistent scores across all 3 sets of data.

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  • $\begingroup$ This is correct: your model is too sparse/simple. To the OP: you should end up with both (a) higher scores across the board and (b) larger disparity between test and train. You're on the right track $\endgroup$ Commented Feb 25, 2023 at 20:04
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The existing answer is a good one - as it mentions you're likely underfitting. What type of model(s) are you using? If for example you're using Linear Regression you might opt for Polynomial instead. Or if the latter is being used you might incorporate some interaction terms . Finally if these do not suffice you might consider richer models like _splines_

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