Bias-Variance Trade-off
[Bias](https://texonom.com/bias-ba063cd622a54deb8a677e8fb87dfdc8) [Variance](https://texonom.com/variance-08c1eccc7dc84957afbb815ad6b41280) 


### Determine model complexity
because this is perspective of model
If a model is too simple and has very few parameters, then it may have large bias and small variance
> It may typically suffer from underfitting
If a model is too complex and has very many parameters, then it may suffer from largevariance but small bias and thus overfitting

### Theoretical background
mean squared error or risk = bias^2 + variance
![](https://www.notion.so/image/https%3A%2F%2Fs3-us-west-2.amazonaws.com%2Fsecure.notion-static.com%2F5d0f7ab4-d570-46ed-ab0b-eb1cf7ed8f1a%2FUntitled.png?table=block&id=29775cf4-8846-485a-b15d-974242966e62&cache=v2)








