What is the electric field due to a line of charge at different distances?

[Amith2006]

Hi guys,
I have got stuck understanding the following problem.
# A straight wire of length L has a uniformly distributed charge Q. Find the electric field on the axis of the wire a distance z from the center of the wire for the cases
(a) z> L/2
(b) -L/2<z<L/2
To begin with, I think they are asking to find the field along the perpendicular bisector of the wire. Also, there are 2 cases to considered. But I don't see much difference between them. Both mean points close to the wire. Have I understood it wrongly? Could anyone clarify it.

 

[aim1732]

I suppose the best way to find out whether they are different cases is to evaluate the general case.