Thought this was cool. Say you need a model for something very difficult to measure…
https://www.youtube.com/watch?v=as0UP2D0AW4&feature=share&list=UUo3oDGvsRWVAbqfvMsJhgVg
https://www.youtube.com/watch?v=as0UP2D0AW4&feature=share&list=UUo3oDGvsRWVAbqfvMsJhgVg