what's wrong the only thing we're to do now is minimize this using one of two algorithm and they're like three things we can do we minimize it that way and then of course our generalization error is just the difference between these two things and so the question is you know if we can compute this one when is that a good or bad proxy for the other one right that's our whole that's what we mean by realization it's a very it's just a badly named term but it's very interesting couple problem and it's kind of like the core problem in machine