Ashwin,
It depends on the communication method and choice of media:
- If we are trying to solve a problem by requesting feedback through surveys or using the Delphi technique, then I would consider this to be "formal written".
- If we are doing the same thing just by sending emails, chats or text messages back and forth, then it's "informal written".
- If we are inviting everyone to a meeting with a clearly defined agenda and timetable in order to determine a root cause, then it would be "formal verbal"
- But if we happen to come across an expert in our company's coffee corner and strike up a root cause conversation with her, then that is clearly "informal verbal".
So you see that the "How" is important. You cannot just simply say "solving a complex problem = formal written" without knowing all the aspects of the communication.
