what is precision and recall?

Question

Watched multiple videos and read many texts including examples and still have no clue

In: Mathematics

Answer 1

Let’s say you have 100 pictures, and some of them have dogs. You write a program that retrieves only the pictures that have dogs.

Your program comes back with 20 pictures. Of those 20 pictures, 18 of them have dogs. So the precision is 18/20 – it’s the number of correct things it retrieved, as a percentage of the total number of things it retrieved.

Your recall is the number of dog pictures it brought back, relative to the total number of dog pictures. So if there were 24 dog pictures, it brought back 18, so its recall is 18/24.