What does it mean if a TI-84 plus calculator says invalid dim?

Answer 1

If you are trying to graph something, it is probably because a stat plot is on and one or both of the lists is it using is blank.

This error will also occur when you try to access a blank list or matrix, or when you try to access or manipulate data it a position of a list or matrix that does not exist. (You can store data into the next open position of a list. If you are editing a list in the list editor, you won't have to worry about putting data in an impossible position)