I will put my site Facebook Chat or Normal chat for users.However, I want to believe that this will be benefical. Is there a graph for that shows it increase pageviews for sites?
I really need it
I don't think you'll find any chart or data showing that a chat room increases the number of users of your site. In fact, it would be difficult to create a chat room going without having enough users there to support it first.
However, if you already have a significant number of users a chat room could be a good idea.
But I don't think you should be trying to link the use of a chat room with an increase of site users, as that is not always the case.