- calculates the total average cost of all the [[Loss Function|Loss Functions]] - $J(w, b) = \frac{1}{m} \sum^{m}_{i=1} L(\hat{y}^{(i)}, y^{(i)})$ - our goal is to find the $w$ & $b$ that minimizes $J(w,b)$ ![[CleanShot 2024-06-06 at [email protected]|400]] - here the height is the cost $J$ - also $w$ will be a scalar in this casesfd