High bias is underfitting High variance is overfitting Generally, we'll want to find a golden mean between the two
How can we tell?
- The training error will tend to decrease as we increase the degree (d) of the polynomial.
- At the same time, the cross validation error will tend to decrease as we increase d up to a point, and then it will increase as d is increased, forming a convex curve.
Summarising
Visually
