machine learning that's why I talk about machine learning and I want to talk about kind of the conventional wisdom that we give to our undergraduates Jonathan here teaches hundreds of them and so I hope I don't know how many of these things you tell them one they're like some how to have a good predictor you have to balance bias and variance alright and that you really should not perfectly fit your training data that's a no-no t something we definitely teach them that in right yeah you have to oh he already knows you don't the punch