Why Overfitting is a Bad Idea and How to Avoid It (Part 1: Overfitting in general)

We want our AI models to be as accurate as they can be. That's one of the selling points of AI -- that we can encode the best version of our past knowledge and have an automated model infer and apply our judgement. How can we tell when the model is accurate enough to trust? More importantly how can we tell if our efforts to improve accuracy are actually making the model worse? This situation can happen through a training problem called overfitting.