Overcoming pitfalls: using NumPy arrays

A local used car company manually appraises each car that they add to their inventory. When a new car comes in, they select from a drop-down menu, giving the car a rating between 1 and 5. A 1 means that the car probably won't sell as is, but a 5 indicates the car will definitely sell without a problem.

With over 38,000 cars in their inventory, the company has asked you to give them an average "sellability" of their cars. For this exercise, use the used_cars dataset. The column of interest is called "Sale Rating" and it is currently a categorical column.